Users should be within their rights to use trademarked/copyrighted terms in the names of their MOCs with free instructions. It sounds like Rebrickable is being bullied by an unjust copyright holder. According to an admin, this copyright holder also “most definitely went through and visually identified a lot of MOCs too” — this may mean in the future you cannot have builds which are too well-made in resembling their source material.

I’ve yet to receive takedown notices for any of my MOCs, but it sounds like this situation is developing so we’ll see if existing names can remain going forward.