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.
What does “MOC” mean in this context?
My Own Creation - a build that was designed by somebody other than The Lego Company.
If you refer to a build that was designed by another person, it can be called a SEC (Somebody Else’s Creation), but it is common to use MOC to refer to either your own or somebody else’s designs depending on the context. Indicating a build is a SEC rather than your MOC helps to make it clear who gets credit for the design.
Thanks!