[Uptown3]

Often, when kibitzing, one would like to be seated when a seat becomes available. When a non-kibitzing player leaves the table, usually another player who has clicked the "Take me to the first seat available" option will be given priority over a kibitzer, so the "Sit" label that would appear in the vacated seat will not appear, because of the speed at which the external player is seated.
I would suggest that the menu within the table includes a "Sit when available" option, and that this option would only appear in the kibitzer's interface.

[barmar]

If you're playing with friends and rotating kibitzers into seats, the simple solution is to enable "Permission required to play".