1. ReVanced has a disclaimer that they're not affiliated, which helps make sure people aren't confused.
2. The Vanced people probably are glad someone's continuing their efforts after they're no longer able to.
3. Vanced has been discontinued and taken down, so it's no longer "used in commerce", so I think the common law trademark should cease to exist.
Yeah, maybe at the piracy trademark comission on pirate island... For obvious reasons Vanced had no trademark on anything and thus can't sue for trademark infringements.
They could possibly sue for a copyright infringement, but for that they'd have to prove that they do in fact hold a copyright on whatever they're suing for. They'd have to prove that (whatever) indeed is either (a) an original work that's protected under copyright or (b) it's a derivative work that's protected under copyright.
Copyright infringement is a much stronger claim at this point if they were actually upset. Vanced obviously had original code, so to the extent ReVanced copies that without permission, it would be infringing.