First, you're discussing edge cases. If people step to the easy stuff a great deal of the problem goes away.
Second, these responses needn't be binary, you can signal a lot of antipathy with body language and conversational subtext. When the commenter is just clueless -- and a lot of these people are just that -- the hint that they're out of line is often all it takes.
I'm not saying settle for subtle when confrontational is called for. But subtle and quiet are frequently all that's needed.
I doubt that "conversational subtext" was the "industry norm" that tptacek intended to advocate, though I do believe that it's not always appropriate to lay the smack down the second you think you hear something offensive.
Second, these responses needn't be binary, you can signal a lot of antipathy with body language and conversational subtext. When the commenter is just clueless -- and a lot of these people are just that -- the hint that they're out of line is often all it takes.
I'm not saying settle for subtle when confrontational is called for. But subtle and quiet are frequently all that's needed.