“This” comments (on Reddit and Lemmy) are not a bad thing. An upvote is supposed to promote valuable content, not necessarily stuff you agree with. A “this” shows agreement. These are different things, and hunting down the “this” promotes the “upvote to agree, downvote to disagree” mentality.

(For example I said “this” to one comment on this thread, which was an unpopular opinion I agreed with. I upvoted plenty of other opinions I found interesting (and actually unpopular) while not necessarily agreeing with them.)