Some moderators on my forum use their real names as usernames. When they issue a warning to a member, a conversation is started with that member and he knows who is the moderator who sent the warning. In case the member is a troll, letting him know who is the moderator could have very bad consequences.
There should be an option in the control panel to define a shared username that is going to be used by all moderators when they issue a warning. This way a conversation will be started by someone called "The Team" instead of "John Doe".