Yeah, there's lots of things about the GMHide feature I do not like. Either it's very precise in it's configuration, or not working quite right. I can be in #gm on mode, and players can do a /who all and see GM-Impossible. I can #gmhide, and I am still there. However, if I turn #gm off (and thus vulnerable to attack) I am no longer on /who all, but now Mobs that are KOS attack the invisible GM.
So many inconsistencies. IMO, the /gmhide (slash version?) vs #gmhideme or whatever it's called, need to be more clearly defined. I do believe it works to an extent, just not fully, or clearly. I'd like any guide/gm to be 100% invisible to any player or /who list (or /tar [name]) simply because that flag is active - not based on any other criteria. Simple.
