From an admittedly cursory reading of Updated comment flagging - Supporting the new Code of Conduct I see that much has been said and, apparently, done about "rude" comments.
Personally, though, I can cope easily with "rudeness" because I just ignore it. But what I find extremely unpleasant to cope with is irrelevance because I feel compelled to answer. Out of politeness but of course also just in case the person making the comment might eventually give a useful answer.
In some cases the author clearly just wants to show off. However, it is most often a matter of the author of the comment not having read the question.
For an example, see my question at Can an air-intake fan stop smoke wafting through a brick common wall?
Question: Is there a way to flag a comment as irrelevant? Perhaps something like: "Please re-read the question"?
Note. This is quite different from How to remove irrelevant answers to posts?