I disagree with locking markers in combat altogether.

To me, they've been an incredibly helpful tool for communication in combat (raids in particular) when typing or voice chatting are not an option (and I'm not a macro person). I can mark safe spots, I can place markers for adds should folks have forgotten about those. I've regularly received positive feedback from other players: "Thanks, whichever player placed those markers!" and felt proud that my assistance was appreciated, but that I could also fulfill my job as a mentor without actually spoiling any mechanics even for players new to a fight.

Locking the markers in combat because of that banned third-party addon makes sense, to me, in extreme, savage and ultimate content, but not the rest of the game. I'd very much prefer to see this lock limited to just that content, or have the lock removed altogether.