Got it - up "up".

Yes, if this sort of chain starts with the admins, they could exploit it for censorship. However that doesn't give them "new" powers to abuse, it's still the "old" powers with extra steps.

And, in this case, the "old" powers are full control over the platform and access to privileged info. Even without this system, the same shitty admins could do things yielding the same dystopia as your example - such as censoring complains through vaguely worded bans ("multiple, repeated violations of the content policy") or exploiting social relations to throw user against user, since they know who you interact with.

So, while I think that you're noticing a real problem, I think that this problem is deeper and appears even without this feature - it's the fact that people would be willing to play along such abusive admins on first place, even as the later misuses systems at their disposal to silence the former. They should be getting up and leaving.

It's also tempting to think on ways to make this system headless, with multiple concurrent chains started by independent parties, that platforms are allowed to accept or decline independently. In this case admins wouldn't be responsible so much for creating those chains, but accepting or declining chains created by someone else. With multiple sites being able to use the same chains.