@BobMastodon It looks like they are on the @oliphant Unified Minimum Block list which we've started to use. That would suggest there's been some serious issues with the instance historically. Let me do some digging to see if I can find out any more on why the instance is recommended to be blocked. It may well be a historic issue that has shifted, or it might be that the instance fails to moderate / administer properly in which case I'd personally suggest your friends shift instances to an instance that does moderate. It's worth saying they're going to be blocked by a fairly large number of instances as this block list is generally trusted as a absolute bare minimum block list and they may want to consider moving anyway for that reason.
I'll take a look probably tomorrow being honest and get back to you.