A global score (karma) is one of those ideas that sound great on paper: you're encouraging people to post better stuff by associating it with some score.

In practice though OP shows why it's a bad idea, on multiple levels. And why I'm glad that Lemmy doesn't have karma.

On some subreddits, we ask to have a Karma in comments good enough [...] (it happened to me on /r/iOSBeta).

Issue #1: enabling shitty moderative practices. Some assumptive = braindead mods think that karma is a viable heuristic to keep trolls and morons at bay. It is not.

Contrast OP's user experience with mine: when still using Reddit I often had a shitposting account, that was never locked out any subreddit due to karma. Why? Because I was willing to game the system and farm karma before shitposting.

And that leads to issue #2: gamified systems are made to be gamed. It's actually easier to farm karma without contributing than to post shit that contributes with Reddit. Repost old stuff, replying comments with shitty one-line jokes (nowadays I'd probably use ChatGPT for that), sticking to high-activity subs (i.e. the worst of Reddit)... you get the idea.

Another problem is users who feel superior to others because they have a better Karma. [...] « You’re a fresh 0-Karma account, you bring proof ».

Issue #3: karma is yet another thing that distracts users from what is said, towards who says it. A user with more karma... has more karma, that's it - anything else is assumption.

In short, I stay on Lemmy.

Welcome back. Lemmy isn't perfect but it's less worse than the options.