Hi, I run an instance.

If I start acting like a jerk, them my users will start leaving. Pretty soon I don't have anyone left except people who like being treated like that. In my experience that will probably mean they're jerks too.

And thus pretty soon my instance is "that instance run by that jerk who lets her users be jerks". At that point, admins on other instances stop federating with my instance. Eventually the only other instances who are willing to talk to mine are also run by and full of jerks, and I am amidst a hell of my own creation.

So that is, as I see it, the external forces acting on me to try and be a chill admin who's nice to her users. It's a lot easier for them to leave my server and stay in contact with people elsewhere than it is to leave Twitter.

I thought we were comparing Mastodon to Twitter where what you say is already the case

Moving instances is not a big deal and yes, know your admin.

One of the ways in which admins often treat instances like their own petty fiefdom is cutting off communication with other instances that don't toe the line. So sure, you can move instances - just don't rely on being able to contact your friends anymore if you do. (Some instances even have a whitelist of instances that are allowed to follow and interact with their users, with everyone else blocked.)

It's rare to outright block an instance (for not moderating child porn or something of course but not otherwise really)

Instead most "blocks" are just muting from the federated timeline, precisely so that you're not cut off from contacts.

How do my followers know to follow me to the new instance? How do they know it’s actually me?

You can mark an account as having moved and specify to where.

Not reliably, and unless your followers are watching for it, they might miss it.