(no one’s going to even see those except me and who I’m talking to).

Untrue. Even one on one’s in a public medium, are public. Lurkers have every right to opine on takes as they see fit, reply or platform-granted reaction tools both. Whether they catch the comments fresh or later when you consider it a “dead thread”.

I personally do it all the time, upvote or downvote.

There’s only so many hours in a day and Fediverse content isn’t so plentiful that it makes sense to mark discussions that are still near the top of a comms feed as “dead” to me.

That’s before we even get into how easy it is to accidentally hit the buttons in a lot of Lemmy client apps.