Also past comments are sometimes better (and other times not) than average. Just depends on who chimes in and their mood and what else is happening in their world at the moment.
As grzm and brudgers pointed out, the goal of such comments is simply to point curious readers to related threads they may find interesting. If there were a problem with the repost we'd mark it a dupe instead. Reposts are fine on HN after a year or so, or if a story hasn't had significant attention yet. This is in the FAQ: https://news.ycombinator.com/item?id=23150065.
I've been looking for a brief, unambiguous phrase that can point people to related threads without having to spell all this out every time. A reader suggested "See also" which seemed like it would hit the spot: https://news.ycombinator.com/item?id=23150065. I guess not!
Hmm, "see also" strikes me as pretty unambiguous phrasing.
I wonder if the problem is that when people are skimming, they're going to to miss a pair of short words in favor of the larger URLs (and by "larger" I mean the physical space the text occupies on screen). A bunch of links to the same post will always seem damning if you don't know better.