@NoNameNowAgain It's not a bit like that. In what do you think it is?
I often go to the cinema alone or with my husband or a friend and unless it's a massive event film where it will be sold out we never book seats but choose from the ones they have when we get there.
We get ourselves settled which takes a couple of minutes and then stay there quietly. One of my friends likes an aisle seat because she has a weak bladder and it's considerate of her to do that rather than to sit in the middle where she'd get a better view but would disturb everyone at least once in the film.
We don't rustle popcorn or chat or look things about the actors up on our phones so we are pretty well behaved compared to many people. It would be really weird to stand up and shout "other seats are available" or anything else except perhaps: "Fire!" but again, only if there was one. Does that happen to you a lot in cinemas or ever? Or did you just dream it?
If the seat next to me or DH or my friends is free we will put our stuff on it. If someone comes along we will of course move it to our laps or between our feet. That's not only polite but sensible. People steal things especially in the dark when your attention is elsewhere. That's not paranoid, that's reality.
There is an exception to this. I love morning screenings on my day off because they are deserted. I have my favourite seat at the local picture house which is in the back row on the centre aisle so has an uninterrupted view of the screen. But I rarely book it, just take pot luck and if someone else has bagged it I'll choose another.
But if someone comes into an almost empty cinema and sits directly in front of you or beside you that's weird, isn't it? Why would anyone want to do that? I have some ideas but perhaps you could say. Would you do that?
If I was alone I would move but if I was with my husband or a friend I would tell them to sit somewhere else. I might even stand up to do it. Wouldn't you? Or would you just sit there because perhaps they just wanted to sit next to you even though other seats were available and you didn't like to say?
It's no different to insisting on sitting next to someone on a bus or a train not because there is nowhere else to sit but because you want to make a point and feel that person is safe to make it on.
I have no problem with sharing public space or giving my seat up to help others. Sometimes I notice and sometimes I don't and people need to ask. I have said that so many times. But as i also keep saying I will not do it just because someone else wants to teach me a lesson or has other motives. If you feel that need so desperately pick on someone else.