Disallow Stun Spore
Disallow Pain Split
Allow Destiny Bond
If paralysis is to be a concern, then I think it clear that Stun Spore is an even more concerning move when we consider that we allowed Gravity. By itself, Stun Spore can still remedy Necturna's low Speed, which is low for a reason. Even at 75% accuracy it will still paralyze (and thus slow) an opposing Pokemon 3 out of 4 times. With Gravity, this becomes a 100% chance for paralysis, and as a plus has no type immunities to it like Thunder Wave does. While it is true that Gravity is not a very popular option to take, it's still there.
I was pretty neutral to Pain Split when I first clicked on the thread. I mostly agree with the negative sentiments to the move (at least, those on the first page).
Destiny Bond is a tough one for me, though. On one hand, this both gives Necturna a way to sacrificially dispose of a counter and presents a deterrent to immediately kill her on the spot.
However, on the other hand, we would see the four-move syndrome kick in if Destiny Bond were to be utilized. I remember when this move was first brought up that if a sweeping set were to carry this move, then they would have a way to eliminate another one of the opposing Pokemon at the tail end of a sweep. The thing is, if someone did that, they run the risk of not doing as much sweeping as they would be sacrificing Necturna. I don't think Necturna, despite all of her perks, is a sweeper who can break through a majority of the metagame effectively with only two attacking moves (Destiny Bond and a setup move would be making up room). In other words, it's sort of the same idea when you consider offensive sets with Substitute. The general idea was that a sweeper would much rather prefer a coverage move than a non-attacking move like Substitute or Destiny Bond.
As such, I think that Destiny Bond provides some interesting utility and doesn't really run the risk of being much of a threat. I would like to see it allowed.