This is a feature I liked on the CompuServe Forums, as a "SysOp". It's not really two lines of code I guess, but transposed to W3T it could go like this:
Moderator can move one particular post considered inappropriate to some particular "Sinbin" board where only admin, moderators, poster and poster of post being replied to could read and follow up on. (If a new thread, only admin moderator and poster.)
The idea is that sometimes there are posts that do are inappropriate, but you don't want to delete, ban the user or anything; you'd just rather have the two posters take this to some private area, where they can tear each other aprat without annoying everyone, and come back when they are friends again (of course it's not what happens in real life but that gets the point across <g>).
Example: Within one thread one particular message is perceived as inappropriate by a moderator, the message is taken to the "Sinbin" board. There the default option is that the message is taken as is, thus becoming invisible in its initial board/thread; appearing as if starting a new thread within a board called "Sinbin", itself within the admin only "$SiteName Administration" Category (as default, then assignable to any other).
So, yes, this would be one particular Category appearing as new to a default registered user in Maind Index (and it would need to somehow look and feel a bit different as this category would be temporary at user level, and appear only until the thread is closed). Then the moderator would probably post an answer to that message, explaining what happened and why, and upon logging in, the receiver of the post (unless it was a new thread) would also see the post within the Sinbin Board, along with the moderator's answer; they could follow up as much as they want within that particular board, which wouldn't be visible to other users, until the thread is closed.
At admin level, of course, all categories are visible, but the "Sinbin" Board, within its admin only category, *only* appears when there is a message actually being sinbined. So the Sinbin Board is some kind of dynamic board (a "stick" option could keep it displayed at all time, and by turning off the Sinbin option it would never appear).
What if there isn't any admin only Category? Then a default one gets created ("$ForumName Administration", with a default description), with only one "Sinbin" board. The Category would default to first one in the Main Index list, and have a slightly different color scheme, including some red, and some kind of "Yellow Card" icon, to give direct implicit explainations of what's happening "You got a yellow card on this message (icon); don't do it again (red color)".
The whole thing would only appear until the thread is closed.
Regarding moderators, I think this should be dealt with as a priviledge. Like:
Can sinbin messages? yes/no
Can see sinbined messages within this board.
Also, "can see Sinbin board" could be assignable on a group basis.
BTW, it's not called "Sinbin" on Compuserve, the message/thread just gets moved to the SysOp section, invisible to normal users, but "Sinbin" came up as I was writing this, and also after that concept (temporary exclusion) was introduced in Northern Hemisphere Internatinal Rugby Union games <bg> where a player getting a yellow card gets "sinbined" for 10 minutes... I extrapolated and thought it could help settle things straight within a Forum environment too, for "offplays", etc. <bg> But I digress, sorry.
Of course, of course, this would assume the ability to move threads across boards and categories, which I can't believe hasn't been part of previous wishlists; and I'm all for it (just this for now) FWIW.
-- mrtn
PS: I'm new to W3T, so please bear with me if I'm missing something obvious here.