I've been on Stack Exchange sites for years, and just in the last week or so I've gotten four comments on answers I've posted that basically say "this answer doesn't add any value" or "this doesn't answer the question". I don't think I've ever gotten such comments on my answers before. I don't know if this is a new trend to make such comments, or if I just happened to have a run of bad posts. :-)
My point here isn't to defend my answers. Rather, my point is to ask, Is there any point in making such comments? (If they're down-voting me, I've accumulated plenty of rep, and in any case my paychecks are not tied to my Stack Exchange rep. And I'm way too arrogant for my feelings to be hurt. Originally I was intending to reference the relevant posts, but I'm not looking for re-assurance that my answers were good. I concede that at least one of them was of minimal value. Let's assume for the sake of argument that they weren't very good.)
In general, if someone down-votes me, I like to see a comment explaining the down-vote. If something I said is incorrect, I'd like to know what the correct facts are. If something I said is poorly worded, ambiguous, or misleading, than it would be helpful to anyone reading to have the point made more clearly. Etc.
But a comment that simply says, "this doesn't add value" or "this doesn't answer the question" or "this is more of a comment than an answer" ... One of the comments of this sort that I got recently had a rather lengthy paragraph about how answers shouldn't repeat information found in other answers, how the system asks you if you've read other answers before posting, and how answers that are similar to other answers or that don't address the question just waste the time of people visiting the site. All of which is true, and even assuming that my answer was worthless: Ok, so my answer is just a waste of space. But it seems to me that a long discussion about why that answer is a waste of space that does nothing to help readers understand the original subject, is itself a waste of space that does nothing to help readers understand the original subject.
On the other hand, I guess one could see value in such a post in that it might inform or remind the poster, and anyone else who is considering posting, that such answers are unwelcome.
On the other other hand though, I'm reluctant to say that any answer that gives accurate and at least arguably relevant information is worthless. I've had a few times where I've felt that someone else's answer made all the important points, but that it was unclear in some way, and so I've posted my own answer in which I say the same thing differently. In one of the cases where I got a "doesn't add anything", I had one small point that I wanted to add to other answers, and in order to introduce it coherently I had to repeat a point that others had made. Arguably my additional point wasn't worth it. Is it more of a waste of space to make a point that isn't important, or to point out that someone else has made a point that you think isn't important?
My feeling is: If you think a post repeats what others have said, so what? Maybe the second person said it in a different way, and this will help some to understand. If you think a post doesn't really answer the question, then unless it's totally irrelevant, like, say, someone asks about putting his grades from college on his resume and someone writes an "answer" about how to bake pudding, if the answer has anything to do with the question at all, I'd think it might be helpful to someone.
I only down-vote when I think an answer is wrong or misleading, and I add a comment saying why I think so.