[elaus]

Because we should strive to improve discussions and pull them up to a higher level if possible. Especially on HN, where the comment section is actually useful instead of a cesspool of empty arguments and insults.

[KingMob]

But saying "This line is a low-effort, cliché dismissal that does not engage the statement in a meaningful way" does none of the things you're hoping for, either.

A much better idea is to down vote and move on.

[000ooo000]

If I downvote a comment, how is the author to know why? If I want to promote thoughtful discussion on HN, downvoting without explaining why does absolutely nothing to serve that goal.

[KingMob]

Not true, downvoted comments get dimmed and placed lower, so the majority of viewed comments will be higher quality.

It doesn't communicate anything to the author, true, but insulting them is still not going to get you any closer to your goal.