I've noticed a lot of commenters straight away take things personally and think that mentioning something is endorsing it. That kills discussion and turns it into a defensive symantic battle against commenters' assumptions.
A corrollary to what you're saying is that people assume that because you've replied to them, you must be disagreeing with them. Often I'll agree with a poster but comment to add to their point, only to get chewed out for disagreeing with them when I didn't.