But people already have a public place to appeal. This sub, the sub you linked, pretty much any other instance that has a meta discussion community. But posting here, or there, isn’t an actual appeal process - it’s just publicly complaining about administrators.

And that was the answer to OP’s question: that there’s no single fediverse-wide place to appeal a ban, you have to follow instance specific appeal procedures, if they exist, and/or contact the instance’s administrators directly.

Which is a good thing, because it helps keep the verse decentralized.

I think, if there was a single location where the fediverse started telling people “if you get banned, post here to appeal”, users would expect some sort of formal response to their post, and get upset when people tell them posting there doesn’t actually do anything. Which would be bad. And if that location could do anything to encourage administrators to reverse ban decisions, via peer pressure or otherwise, that would also be bad, because it would compromise the independence of instances.

So I think the only appropriate response to “I was banned, what can I do” is “that’s between you and the people who banned you”.