The "reasons" Github offers for minimizing comments are: Spam, Abuse, Off Topic, Outdated, and Resolved. "+1" isn't exactly any of those. (I guess they're kinda "Spam" but they're not unsolicited commercial messages.)
(Personally, I would consider them spam.)
I also think they're still valuable when you have Github and another VCS host, where one mirrors the other automatically.
I was astonished that they didn't do this when they introduced the emoji reactions feature.
I think it could be done on a per repository basis, like, basic behaviour rules just like at forums and other such communities. It's then up to the maintainer / moderators / whatever to allow or disallow +1-style comments, and what the 'punishment' would be. They could then also tweak a setting that auto hides comments if they're shorter than X characters.
Well then the user would learn nothing. A better solution would be to notify them that this is wrong, delete their comment, and then prevent them from commenting on github.com for a period of time (1 hour? or more?)
If you don't have anything more to add to the discussion, but it seems like the issue is not being considered, a "+1" comment seems like the most effective way to communicate the need to the devs.
Ideally a thumbs up reaction would do the same thing, but does it? Do devs use the sort by "reaction" feature in real life?
I have not yet had the chance to be on the other side. I'm pretty sure I'd check that list occasionally, but I bet I'd forget a lot of the time. Especially if I had a busy project. Sorting by "most recent" or "number of" comments would be more likely. And that would make a "+1" comment more effective.