Christ, I'm not really on the 'complain about social media' train, but this resonates with me so much. The way people pose and mug for upvotes on Reddit - or mortifiedly delete their comments when they get some downdoots – is, well, it's self-abasing. I can't believe the effect it has on people. For kids I can only imagine how destructive it would be, in the already insecure and reputation-centric environment of school.
I don't know what the solution is. I believe it lies _broadly in the direction of_ better clients, rather than different networks. The latter is a fool's errand. The former is still hard, but at least practicable on one's own: to find or create [apps / web clients / browser extensions / etc] which don't surface the karma component as much.
HN is a good example of that: it still has upvotes and downvotes, but the design (especially not showing you others' downvotes, beyond binary indicators of positive/negative) centres them much less. It's an illustration of how you can substantially reduce this through frontend changes alone, without needing to change the core logic of the product.