You can literally see everyone's instance right next to their name on most Fediverse clients - I'm Michał "phoe" Herda, but also @phoe@functional.cafe, which already gives people one more possibility to choose from as long as they see my posts pop up. Then, there's some independent instance browsers, and, finally, you can just ask a #question in a public post and ask for boosts.

> As for contacting your admin to say you think they're being petty... Do you think that would work?

Yes. I'm a mod on functional.cafe, we've had a few instances of our users contacting us with moderation questions and we've asked our users for feedback several times as well, and we've managed to resolve them to almost everyone's enjoyment. I'll probably repeat - if you can't trust your instance admin, then it's on you. There's no higher authority to appeal to, so quite literally the only option is "if you don't like it, you can leave", except you have hundreds of choices with distinct moderation policies.

It's the same as with great migration - if you ended up on an instance that doesn't resonate with you, then hopping to another one is even cheaper than it used to be (with the new "account moved to" feature that, AFAIR, wasn't there during the great migration).

Finding a good instance that suits you well isn't exactly cheap; you're not a product, meaning there's no one who makes money on you always having a good initial experience. That's the cost associated with the meaning of you being a person, not a product - you need to find your place in society, and there are instances as generalist, specialized, bland, and wicked as you can imagine for you to choose from.