Sorry, but to finally address the OP, as of right now the plan is to handle these on a case by case basis. We’re not drawing any bright lines. This is our usual policy.
I can easily see calling a specific group invaders being a moddable.
I don’t really see “illegals” as used in that thread as being moddable. But a reply that explains why the usage is offensive without going after the poster that said it is well within the rules. If it turns into a back and forth that hijacks a thread, all posters will be advised to drop it or take it elsewhere.