“If the table is that uncomfortable just squash in somewhere you are more comfortable no-one minds squashing, it’s all very acceptable.”
You miss the point. a) I did not know ANYONE else there and b) you are mistaken if you believe that no one minds squashing. Yes, they do. Very much! It is not acceptable to show such poor manners as to leave your table and make other people uncomfortable, just because you feel like it. I can see kids doing that (and they shouldn’t), but a mature adult does not play such games. On the other hand, if there are tables with empty seats and no one objects to someone joining them, as often happens, that is a different story. But that does not help when you know no one else at the simcha.