I don't flag comments very often unless they egregiously break the rules, but I've downvoted things like this before. Usually what happens is the person gets upset that they've been penalized by the system if the downvotes stick, or someone comes along and actually thinks the comment is good, and the effects of downranking it are reversed. I don't want to propose that my opinions on comments should overrule everyone else's, but I know you agree that just because people upvote vapid or clichéd content doesn't make it appropriate for Hacker News. So, I haven't really found your solution to work in practice.

What I could absolutely do is sit down and write a long reply about why I think the comment missed the mark, and how it could improve. I have done this in the past too. The problem here is that doing so is a lot of work. My thought process is that most of the people who are posting like this know that they're just posting low quality stuff, and if there's an easy reminder to stop doing that, they will. If they happen to reply with "no, I'm serious, here's why…" then there's no harm done; otherwise it signals (to other people too) that we're looking for something better than that.