If creating an identity has a cost, then why not allow people to own multiple identities? Might help on the privacy front and address the permadeath issue.
Of course everything sounds plausible when speaking at such a high level.
I agree and think the ability to spin up new identities is crucial to any sort of successful reputation system (and reflects the realities of how both good and bad actors would use it). Think back to early internet when you wanted an identity in one community (e.g. forums about games you play) that was separate from another (e.g. banking). But it means those reputation identities need to take some investment (e.g. of time / contribution / whatever) to build, and can't become usefully trusted until reaching some threshold.
Yep, this is basically how I'd implement it if I needed to. Just tackle the problem in reverse here: Don't assume users are good and try and track which are bad, assume users are bad and track which are good.
Look at the HN karma system--you start with limited features, and as you show yourself a good user, you get more features (and also trust/standing with the community). "Resetting" your identity only ever loses you something.
Apply the same thing to a git host getting hammered or something--by default, users can't view the history online or something (can still clone), but as your identity establishes reputation (through positive interactions, or even just browsing in a non-bot-like manner), your reputation increases and you get rate-limited access or something.
This is essentially where a lot of spam ended up--it used to be that your mail was deliverable until you acted poorly, then your reputation was bad and your deliverability went down. Now it more closely resembles this--your reputation is bad until you send enough good mail and take enough good actions (DKIM/SPF, etc) to show yourself as good.
The issues really all stems from "resetting your identity gets you back in good standing". Once you take that out of the mix, you no longer need to worry much about limiting identities, tying them to the real world, ensuring they're persistent, or many of the other hard problems that come up.
Because of course what this world needs is for the wealthy to have even more advantages over the normies. (Hint: If you're reading this, and think you're one of the wealthy ones, you aren't)
Of course everything sounds plausible when speaking at such a high level.