Marshall has copyright on his lyrics, you just said yourself patents and copyright are different things.
Sufficiently different rip-offs that don't confuse consumers as being the original should be legal. They already are as far as copyright is concerned.
Many design patents should never have been registered, and should lose when defended in court. Design trademarks are a third similar issue.
It's good for email and personal sites (those aren't dead, but they're more popular for people that either write a lot or are self-employed). I'd only use a personal domain for self hosted apps if the users are just you and your family.
For something like hosting Lemmy, with users you don't know, I wouldn't use the same domain as where you host your other personal stuff, even if it's not your name.