I'm a furry, furry is a community built around an isolation between our IRL identity and our online one. But the community is tight knit enough that your reputation will follow you around - the identity you created for yourself yes - but still your identity, and if you're too far out of bounds, you get quietly (or loudly) excluded from the mainstream of the community. It largely functions the same way as tying your real name to every online identity.

Now take something like twitter - you start with a karma of say 75, anything less than 100 karma, and your tweets wont show up in searches, anything less than 50 and you start to disappear from timeline - even for followers, anything less than 30, you disappear from lists - effectively this creates an automatic shadow banning system.

But a saving grace, you earn a quarter point of karma just by not having any negative interactions on the site, you could also earn positive karma by upvotes on content.

You could also put some other bounds in there too, like limiting how much positive karma or negative karma a single post could earn, to prevent it from skewing the numbers too much (it should be based on a weighted average of interactions, not just on one tweet that goes viral and the rest of it is low effort shitposting).

Ideally you'd have a cross site 'identity' service that would also carry along a weighted karma score from all of the places you interact, and allow people to see those links - you're still abstracted from your real identity, and you're always welcome to start over again, abandon your account and start from zero, but there is persistent history of your interactions.