Why would key delegation centralize anything? PGP has key delegation without issue.
Discussion
...and yes, putting tweets on a block chain/git style data structure is a very good idea. That's how you can easily find out how much you've actually seen, and what you may have missed or been censored from seeing.
It just doesn't work in practice. Scuttlebutt users and developers suffer every single day with forking histories and the inability to use the same account in multiple apps or devices.
Who decides what keys have been revoked or not?