I have seen some DTs have red tagged few people for trolling but it should not be tagged in my opinion.Those kind of trolls needs to be banned because it is against the forum rules but tagging them be like using their power on someone who don't like.
I don't think it's in the rules that trolls shoukd be banned from the forum,if it is I stand to be corrected,the problem is there are different kind of trolls and one or two minor trolls which almost everyone does is definitely no issue and should not attract any ban.
But when one consistently trolls and argues a case incessantly against the community it then becomes hard for us to ascertain their sanity and hence we need to warn others of them,cos you may never know in real life they could be mentally unstable.