

What’s the actual point of holding someone back from joining your online community if they don’t have enough “points” on their comments or posts?
It is a legitimate anti-abuse tactic. Like you’ve mentioned, there are obvious flaws, but it does help prevent brigadiers, advertisers and other bad actors from easily spinning up throwaways to harass or manipulate a community.
Another way to do this could be account age testing, but this can be defeated by pre-registering empty accounts.

Perhaps its too late for the largest instances, but the idea of a site like this being a spectator activity, about consumption, rather than creating communities. Some smaller instances, and even some larger ones, have an actual unique atmosphere and have larger projects across the instance. When we suddenly got a flood of reddit users escaping from the third-party API fiasco and the Luigi bans, that was huge enough to dilute some of the communities with large amounts of people used to simply voting and commenting, or having a website premade for them.