It seems so obvious, and yet it always surprises me.
I seem to have a built-in assumption that what I say with one person will remain with that person, and be separate from what I've told another person. Like I keep track in my head who I think knows what, and the impression I think someone has of me is based solely on my interactions with them.
Whenever it becomes obvious that they have been talking to each other when I wasn't there, particularly if they have been talking about me, I get a very 'cold' feeling, like the worlds I had thought were separate are colliding in an unpredictable manner.
I don't know how to tell what people think of me, so I try to interpret what they might think of me based on the 'logical' consequence of what I've said/done/etc. while around them. When they are getting information from another source that I have no control over I lose track of this 'state' and don't know how to pick it back up again.
I suppose the only solution to this is to behave absolutely consistently around everyone, so everyone shares the same impression, but I don't really see how that can work in practice either, surely the level of information you can share with someone should be based on your perceived level of intimacy.
Of course since I don't really know what impression people have of me at all, maybe I am just being excessively paranoid, an I am in reality much more consistent than I think I am, and it doesn't matter.
Actually now I think about it more it seems my 'Theory Of Mind' treats other people like a 'Hidden Markov Model', I can observe the output (words, actions but not body language), control my input (only so far as I am aware of my own appearance, so I don't know exactly what input my facial expressions and body language are contributing), but cannot detect their current state nor determine the state transition probabilities except through long periods of observation.