I'd always assumed the intent was to vote when you feel something contributes to the discussion, or is particularly relevant.
For example, upvoting when a subject matter expert gives some context, or the person offers a comment that you found interesting. Conversely downvoting when there is a "me too"/contentless comment.
Personally I most commonly find myself downvoting what I would describe as either rhetoric or offensive.
"I'd always assumed the intent was to vote when you feel something contributes to the discussion, or is particularly relevant."
It is. I've decided to just leave the comments (reactions) as they are and signal upvote by commenting. If the post/comment is of no interest, no comment. Voting in some ways has distorted the real intent of the site: "talking about things hackers like".
Imagine of the rating system did away with votes and instead measured the quality of the discourse on something interesting.
For example, upvoting when a subject matter expert gives some context, or the person offers a comment that you found interesting. Conversely downvoting when there is a "me too"/contentless comment.
Personally I most commonly find myself downvoting what I would describe as either rhetoric or offensive.