the point at which it's actively harming someone else / someone else's fun, and you've exhausted reasonable accommodations.

ex: as a mod, you can try to offer options if someone's math dyslexia challenges them to keep track of and add up their monthly AC.

ex 2: you don't need to excuse someone who is aggressively ship pushing because they're so depressed right now, and this pairing is the only thing that gives them joy.