I almost let Outlaw and AG's forfeit stand. I really did. While it's true that it would heavily skew the game in favor of Austria/Italy, who would be able to pick up the supply centers left behind fairly easily, forfeit is allowed in the diplomacy rulebook. Essentially, the dilemma was my own personal principles of "the game must go on" and desire to sub those who no longer wish to play in exchange for those who do, versus the actual rules of the game and the wishes of the two players in question.
Here's the thing though. The manner in which AG and Outlaw conducted their forfeit was incredibly unprofessional. The term "rage quit" was thrown around a lot in #thegame in the aftermath, and while this term may be a bit strong, the manner in which Outlaw and AG left was frankly embarrassing. I realize it's frustrating to watch a player make gains and be unable to do anything about it, but come on guys. It's a game, and one in which you two are rather respected members of the community. Hell, Bass even said that he bases his playstyle around Outlaw's.
The other argument that was made in favor of the forfeit (by AG specifically, Outlaw hasn't reached out to me at all) was that it would be essentially the same maneuver as moving all of their troops to combat England, thus leaving their flank exposed for Austria and Italy to waltz in. This is a fair point, and one that I rather strongly considered. It's true that I would have been much less likely to sub them out had this been what they done. However, this would have at least required them to actively take involvement in the game. If they really wished to combat England, forfeiting was the much lazier and (in my opinion) least effective way to do so.
Which leads me to my final point. I can believe that Aura Guardian's sole purpose in forfeiting was to help the rest of the game combat England, and I can believe that AG had been planning on forfeiting already anyways (playing as Turkey and getting stuck at Bulgaria is never a fun experience). However, Outlaw's phrasing and conduct strongly suggested to me that he disapproved of the way I ran my game and may have acted with the intent of impeding the game's progress and harming its integrity. Outlaw, you made some good points about the dangers of substitutions, but there are ways to voice this disapproval without fucking with the game as a whole. In the 3+ years I've been hosting games on Circus Maximus, I've always tried to prioritize the continuation of the game and fun for all involved players above other aspects, and that's not about to change.
tl;dr it's my game and I'll run it how I want tyvm