Would such buttons be used or useful at all? Is expressing your opinion in general useful? Won't such buttons be even more susceptible to the humility issue? Is it just a problem of showing up?
There is an argument to be made, I think, that merely the fact of your wanting such features is evidence of their being likely to be used, but I do feel it should be made rationally beyond, "This would be cool for me."
I do not deny that such a thing is useful, and I have thought about it considerably, even to an implementation level, but I question if it is the solution here. I don't think it is.
One possible value of more diverse buttons would be more specific feedback to the comment author, as well as providing data to all participnats about what type of comments "do well" here.
As it stands, highly upvoted comments appear to me to mean the group agrees, strongly downvoted comments just disappear & comments with low votes are ??? (possible answers: ignored, too technical, wrong, redundant, obvious, disagreed with but not strongly, poorly written but so poorly written that no one wanted to make fun of that guy, late to the discussion...
Every now and then, I write an LW comment on some topic and feel that the contents of my comment pretty much settles the issue decisively. Instead, the comment seems to get ignored entirely - it either gets very few votes or none, nobody responds to it, and the discussion generally continues as if it had never been posted.
Similarly, every now and then I see somebody else make a post or comment that they clearly feel is decisive, but which doesn't seem very interesting to me. Either it seems to be saying something obvious, or I don't get its connection to the topic at hand in the first place.
This seems like it would be about inferential distance: either the writer doesn't know the things that make the reader experience the comment as uninteresting, or the reader doesn't know the things that make the writer experience the comment as interesting. So there's inferential silence - a sufficiently long inferential distance that a claim doesn't provoke even objections, just uncomprehending or indifferent silence.
But "explain your reasoning in more detail" doesn't seem like it would help with the issue. For one, we often don't know beforehand when people don't share our assumptions. Also, some of the comments or posts that seem to encounter this kind of a fate are already relatively long. For example, Wei Dai wondered why MIRI-affiliated people don't often respond to his posts that raise criticisms, and I essentially replied that I found the content of his post relatively obvious so didn't have much to say.
Perhaps people could more often explicitly comment if they notice that something that a poster seems to consider a big thing doesn't seem very interesting or meaningful to them, and briefly explain why? Even a sentence or two might be helpful for the original poster.