There's a general problem here, for which I'll give a specific illustration, but this is about the general problem, not any one instance. We see many useful comments where the commentator makes reasonable points, then their shoulder devil somehow can't help but toss on some condescending and not-nice trailer.
Useful sentence. Useful sentence. Snide comment. - Mr.Foo
My impression of the usual policy here is that readers are to promptly flag such comments, so that they can be deleted, but too often that would make the surrounding comments seems less coherent. Given the choice, it might be preferable to have a kind of "snide-item veto", where we could just flag only the snide bits, and leave the rest standing so that the commentator's intelligent side would outlast any momentary piques.
Because of the current all or nothing model, before flagging, I find myself weighing whether a deletion is worth the loss of a comment's intelligent parts. If the commentator is thereafter polite, it's a win. If the commentator devolves further it's a loss. Snideness can be somewhat contagious, setting a bad example that other commentators emulate.
Here's an example from yannis, who'd be happy to help find an example if my memory were better, but he can only do so much. The first three sentences were fine.
The fourth sentence (italics mine) is snide, characterizing such efforts as "waste", and the fifth (bold italics) is even more snide, implying my memory is not merely sketchy, (a point readily conceded prior to this comment), but wrongly biased:
@agc No. You went through the trouble of posting a very specific complaint about SE moderators. If there's anything of substance to this, point me to the right direction and I'll gladly dig up deleted comments and post them in an answer here. But I'm not going to waste my time looking for comments that "might apply" to your hypothetical. Especially since I very strongly doubt that your hypotethical is anything close to accurate. – yannis♦ Jul 31 at 9:54
A hypothetical snide item veto might reduce that to:
@agc No. You went through the trouble of posting a very specific complaint about SE moderators. If there's anything of substance to this, point me to the right direction and I'll gladly dig up deleted comments and post them in an answer here. – yannis♦ Jul 31 at 9:54