A good question, but not one that's easy to answer cleanly.
It is those who choose to interact with a scene via stealthy means that typically require staff involvement (because they could be found out).
On the one hand, if a character attempts to call or knock at the door, this can be handled IC by the scene participants. On the other hand, a suspiciously perfectly-timed call or knock
could be considered metagaming. How would one character
necessarily know the exact time to interrupt, in order to interact with a scene in-progress? The same applies to Tribal forums. The timing of the "thing" a character wants to walk in on must be known IC by the interrupting character as a prerequisite. "I just happened to be walking by" is weak, and generally not acceptable.
If, for example, a scene starts with "There's a howl across the sept for all Silver Fangs", then anyone who's around pretty much knows that the Fangs are meeting, and it's ok to
openly walk in on that scene, with IC consequences understood to be likely. If means of being stealthy are being used by the scene's participants ("cone of silence" through Gift or Ritual, etc.) then this should be noted in the initial thread, and that scene would be off-limits outside of working with the staff.
Similarly, it may be perfectly appropriate for a Glass Walker to post in the Bone Gnawer Tribal forum, for example, if the Glass Walker is starting the scene and it is his/her intention to find/interact with (a) Bone Gnawer(s) for something. In this same way, people showing up randomly at Masha's house to start a new scene would be just fine, as long as they call or come to the door. A precedent was sort of set for this with the Soloman Estates forum, whereby people who don't live there generally start new threads with an "arrive at the gate" post.
It is only when people start showing up in the middle of presumed Tribe-restricted scenes (that they have no way of knowing about IC), or start posting that they just happen to be in your living room, that there may be a problem.
This rule is intentionally vague to capture all of the possible nuances-that-could-be. There are many variables based on circumstance, as to what should be presumed private, and in what way. In most cases, common sense should prevail.
![Smiley :)](http://rageacrossthecape.com/forums/Smileys/default/smiley.gif)