You can edit it by going inside your .grf and editing the monstertalktable.txt or something like that. As for its "legality", I'm not sure about that but I don't see anything wrong with it at the top of my head.
Or you could turn off your Public Log. The one at the top when you edit your chat dialogue box. The only caveat of it is it's on the same channel as the main chat so you won't see that as well. You could alway make a separate tab for it. Or better yet, get off the map heh.