Lately on PVE4 I have had metal signs edited frequently containing profane language and now bigotry. Honestly I am not offended by it in the least bit, its an easy fix when I login again. However I feel like if the chat censor can block certain words, you would think that they would be able to detect them on objects in game. I know I'm not the only one, but I seem to get targeted a lot; maybe I get targeted because I set up my base to help others and people can't handle that. There's no evidence to indicate who edited the sign unless they sign their name, lol, but I would imagine that if it is typed that the server would have a log of it. Maybe I'll throw my hat in for moderator/admin, seem to be scarce on PVE4.
It's someone in the same group as you if both you and the offender can edit the metal sign. Consider creating your own steam group which you can moderate. Allow only trusted players into that group.
In Unturned I am not part of a group, is not being in a group considered a "group" (of independent players)? I do belong to a Steam group but we do not have any official presence in Unturned; that doesn't mean that there may not be someone from my gaming group playing on their own like myself.