Idk, you can abuse everything. Does that mean nothing that could be abused should exist?
I expect them to at least verify that you're doing some useful work on GitHub. If you are, I don't even particularly mind you exploiting this, even if it's perhaps not ideal.
> everything being centralised means one party now has control over multiple communities
Which is precisely why I started working on a federated alternative that uses ActivityPub to let users essentially build cross-server homepages of their own.