No, comfort is not guaranteed, but some basics of comfort are assumed, mainly that you get some space to have as your own, hence the armrests.
So that I dislike someone coming over the armrest and touching me is not so outrageous after all.
You might want to consult with an attorney first to see what your chances would be of succeeding, though.
I'm betting rudeness still isn't a good basis for a lawsuit, but maybe we've fallen so far that it is now.
Some of the biggest space hogs around are skinny women who think they are God's gift to the world. Whenever one of these hags starts playing her role, I give her the what for with my elbow. She always acts shocked. Give me a large sized person who is considerate and at least tries to share the space over some bimbo who thinks she owns the place.