Many block only hexbear and lemmygrad because they are just propaganda machines. Mostly they were left unblocked until their users started to invade other instances to spread their blatant propaganda.
I think if it like an ad block. On lemm.ee, I blocked them both on my own anyway because I found them obnoxious.
If you go to the main page website of an instance and scroll all the way to the bottom, there should be an "instances" button that will tell you which instances are federated and which are blocked. I figure the default page is like lemme.ee/instances or sopuli.xyz/instances for example.
edit: I've upset the .ml Also, you'll see most have chapo.chat is also on the blocked list because it is Hexbear when Hexbear lost their server or something
The letter agrees. It's too unpredictable AND adds that what he's doing hasn't been done so they really have to comparison