The thing is that, at least the way me and the other pro-GT ban people see it, Gorilla Tactics IS the root of the problem for Darmanitan (the only user of the ability that currently exists) specifically. When forced to use Zen Mode it is not even close to being as overpowering and centralizing as the current Choice Scarf/Band sets are. The near total lack of defensive counterplay, the absurd damage output, that all comes down to Gorilla Tactics. I personally feel that it is far more arbitrary to ban Zen Darm when it is so blatantly not a problem and will be even less so after a GT ban when it won't even be able to use the surprise factor and constant threat of the GT sets to pull off its Belly Drum + Salac shenanigans.
Can we finally get some council members to weigh in on this debate? I think we've kinda reached an impasse and it would be best for them to throw their hat into the ring so we can maybe get somewhere.
Lower tier precedent is important because it gives a more complete look at the history and methodology of rulings. There are more tiers than OU with just as many valid balance concerns which necessitated bans. I'm against collateral mainly because I play lower tiers. So yes, do think "irrelevant" mons matter in OU rulings. Which is getting sidetracked since the argument here is that there is no collateral with GT. The discussion at hand isn't Protean dinging Kecleon, it's G-Darm being overpowered, GT being what makes it overpowered, Zen not being overpowered, no other mon having GT, and a discussion about a ruling that specifically targets the unhealthy aspect of Darm's role in the meta. People are arguing against this by bringing up Blaze Blaziken (complex), Protean instead of Greninja (collateral), and arbitrary ability power tiers (irrelevant since balance affects what actually exists, not theorymon).
So honestly I'm completely unconvinced by the arguments against a GT ruling. The best counter I can think of is setting a nerf precedent but that falls on its face when you realize the amount of factors that need to be in place for future arguments to gain relevancy like this one. A broken mon would need to have: 1. An ability that adds an extreme power boost, 2. A signature ability that nothing else gets, 3. A secondary ability to make an ability ban not just a mon ban with a different ruling, and 4. An unarguably unhealthy effect on the metagame caused by that ability.
Gorilla Tactics doesn't exist without Darm, Darm exists without Gorilla Tactics. Darm without GT isn't broken. Therefore GT is the issue. Seems like pretty simple logic. I'm kind of sick of the "inherently broken or balanced" argument. Look at what's actually around, not what could be theorymonned.
Fairy Aura and Dark Aura are strictly worse than Adaptability in singles, but manage to be stronger abilities in practice. Same for Arena Trap vs Shadow Tag in gen 5 -- the former was banned, but Shadow Tag is still legal. This has never been a problem for tiering policy, because distribution is an aspect of the ability, and being given to better Pokemon is something that makes an ability better. We ban things because of the actual problems they present in this metagame, not because of the problems they might theoretically pose if they had better distribution. It makes no sense to insist that OU uses Balanced Hackmons tiering policy, because we aren't playing Balanced Hackmons.
(For another, admittedly very facetious example: we don't ban Primordial Sea in tiers where Drizzle is banned "just for consistency" if nothing in the tier actually gets it. We accept that banning Primal Kyogre in UU accomplishes the same thing in practice.)
So what you're saying is that Shadow Tag is banworthy because it's broken on everything that gets it. This supports my point just as much as it counters it. I'll admit that the existence of a 30BST Pokemon with STag wouldn't mean we had to ban every STag Pokemon because a non-broken instance of the ability existed, though.
I can appreciate the difference between an ability being banned for being uncompetitive vs being banned for being overpowered, but I'm not convinced that it makes a difference in terms of how we should handle it. Generally, the reason we ban uncompetitive abilities outright and not overpowered ones is that their orthogonal angles of attack mean they produce similar metagame problems on their weaker users when the stronger users are removed. Gothita STag and Arena Trap Diglett are good examples of this.
I think your stance is that uncompetitive abilities are disallowable in isolation, but this is not consistent with how we have handled those abilities in the past. Heck, even in this generation, we didn't re-ban Moody just because it is conceptually uncompetitive. We banned it once it started producing regularly good results in high level play with the right roll. In the case of both Moody and STag, we saw the actual material effect on play before making a difference -- something which inevitably takes distribution into account to a degree, because the abilities will obviously only be used on things that can legally get them. In short, I think we have handled uncompetitive abilities differently because they tend to be problematic on every user, not because of a core difference in tiering philosophy.
Conversely, Galarian Darmanitan is good and fundamentally sound, but too good when paired with Gorilla Tactics.
The difference is that Gorilla Tactics is, by current legality, not capable of not coexisting with Darmanitan-G. Darmanitan, however, is capable of not coexisting with Gorilla Tactics, and is probably not overpowered when it does.
I don't think these are good comparisons because none of these things are signature abilities/items. There is a choice between two sets of collateral damage for keeping the ban simple in your examples, and that's not a factor here. There would be absolutely zero difference, other than allowing Zen Mode Darmanitan, if we banned Gorilla Tactics, and I think that makes Gorilla Tactics something of a special case.
The fact that there are zero non-broken instances of Gorilla Tactics is important. Sure, it's that way because only one thing gets it, rather than because it would be broken if other things got it, but it's not at all self-evident to me that tiering philosophy should care *why* it's broken on everything that gets it.
I would also argue that Speed Boost is the root of the problem, rather than Blaziken -- it's inherently a very good ability, whereas Blaziken is a fairly mediocre Pokemon in isolation. Feel free to correct me here, but I think we chose to ban Blaziken because tiering philosophy is to prefer banning Pokemon in cases where conflict between two sets of collateral damage exists. So I think the lack of any collateral damage is important here: it's more like the Mewnium Z ban in UU last gen, which was banned for power level reasons and was banned instead of Mew because the non-broken element could be preserved by a simple ban with zero collateral.
I will accept, in the interests of fairness, that there might be precedent for not banning broken signature elements and banning the Pokemon instead. Marshadow springs to mind, but I don't know if Spectral Thief would have been considered for a ban if it wasn't for Smeargle existing. It probably would have been seen as a pet nerf, even though Spectral Thief offers unique functionality. I feel like moves and abilities/items ought to be treated differently here, but I readily accept that there are grounds to disagree.
Edit: another factor that just occurred to me. We tier certain things differently in order to tier different forms separately, such as banning Power Construct or certain Mega Stones. Is it worth doing the same to *allow* a specific form? Should we be trying to preserve Zen Mode Darmanitan-G as a different form, even if we would not otherwise try to preserve an alternative ability? Or does the fact that the form change is battle-conditional preclude this?
Basically, what qways said. Tiering policy dictates we ban the problematic Pokemon first, regardless of its distribution. Just because this wasn't done consistently in the past doesn't mean it's not supposed to be how it's done. Ability bans are only done in extreme and rare cases. Shadow Tag was such a case.
Rarycaris uncompetitiveness was absolutely cited as one of the reasons for the re-ban of Moody, because even though it lost Evasion, it was still entirely random and unpredictable to an extreme degree. It's even in the official post about the ban. That's why the ability was banned regardless of the tiers the ability-holders are in, while the only abuser in OU was Glalie. Nothing about Gorilla Tactics itself is uncompetitive, and any logic you could try to do so would have to extend to Huge Power as well since it's a strict upgrade. Distribution, according to tiering policy, is NOT an exception, and before you cite Power Construct, may I remind you that said ability was banned only because it gave Zygarde access to, what was in essence, an entirely different Pokemon: Zygarde Complete. The form itself was what needed to be quickbanned, the ability was just the route to getting there. If Zen Mode was what we were discussing here, I would actually argue in favor of the ability being banned by the same reasoning. But that's not where we are.
Also, Fairy and Dark Aura are NOT "better in practice" in Singles, and I'd argue only situationally so in Doubles. They're simply on stronger Pokemon. If Xerneas and Yveltal had Adaptability instead, they'd be waaaay more powerful. Obviously they don't under normal circumstances, and their abilities still make them more powerful than with no ability at all, but the same can be said with nearly any ability, short of strictly inhibiting ones. It is Xerneas and Yveltal that are too problematic for OU, not their abilities directly, although their abilities help, and while they're more extreme than Galarian Darm, the same point can still be said. If, in the future, another Pokemon came along that had Gorilla Tactics, would we have to ban that Pokemon's use of Gorilla Tactics as well, even if it had worse stats, typing, and movepool? Probably not. Nothing about Gorilla Tactics would break said hypothetical future Pokemon or make it uncompetitive, and therefore the precedent set by banning Gorilla Tactics now with no foresight would be entirely useless. This is why tiering policy mandates we look to the Pokemon first. Shadow Tag, on the other hand, along with Arena Trap, proved itself time and again to be uncompetitive by its own very nature. This is why Shadow Tag was banned, and not individual mons like Wynaut and Gothitelle.
Shadow Tag's ban is an extreme exception to the rule related to an inherent flaw in said ability itself, as with Arena Trap, while Power Construct's ban was merely a side effect of having to ban Zygarde Complete. There is nothing inherently flawed with Gorilla Tactics, neither is there with Galar Darmanitan, but the two combined are too powerful, and Tiering Policy bans the mon first and foremost in all cases so that when new Pokemon roll around that also have said ability, that Pokemon won't lose access to said ability by extension.