I'm not interested. I've got enough going on as it is; I really don't want to feel obliged to deal with 'informal (chit-)chat'. I took a quick look at the M.SE. chat room and quite a lot of it seems to be the usual meandering and idle conversations. I would feel free to ignore an analogous chat room here and any attendant fluff if I weren't a moderator. But now you want me to have to tune into this?!
More importantly: what of substance would be accomplished there that couldn't be accomplished through the means we already have (MO meta, flagging, and moderator email)? Many issues having to do with spam and troublesome users require care and sensitive and discreet handling, involving actions that are best handled privately.
Furthermore, I think this post is going about it wrong: this is something that you should really ask the mods about beforehand. Putting this up for public discussion puts us mods on the spot, and I don't like that one little bit. (Let me clarify that last sentence. I believe that an "MO Mods' Office" chat room, being somewhat of an imposition on the time, energy, and attention of the moderators, is not something to be imposed on the moderators by popular demand through a public discussion -- it absolutely has to come on offer from the moderators themselves.)
Added later: Someone I know on the SE Team also points out that while other SE sites may have such chat rooms (which by the way are initiated by moderators, not random users -- as it had been in this case as I comment below before I asked the user to take it down), it's probably not a great idea because it makes it way too easy for stuff to get lost.
Added still later: Partly in response to Asaf's comment, let me more prominently display the MO moderator email address, in case people feel the need for a private chat with the moderators that doesn't fit conveniently in a flag message and isn't really fit for public consumption at meta. It's
I like to think we respond to emails in a fairly timely fashion. Asaf and quid (to name just two) have been known to take advantage of this option and I hope it works well for them. But it's not an option for people who just want to "shoot the bull" (where 'bull' is short for something) -- we're just not that kind of moderator team, I guess. (Sometimes people have been known to reach just me as well -- I think my email address is not hard to discover -- but I think the address above should mostly suffice.)