BUT, if one person is sitting in a quad of four seats with the double seats facing each other, it is obnoxious to sit down directly across from the woman who was already there, knee to knee, when she could have sat down catty corner (diagonally) across from her in that empty seat instead.
ANYONE who rides trains with any regularity knows the quad seats are TIGHT. when you say "knee to knee" you mean TOUCHING, there is simply no way around it, unless you have a manspreader across from a person in a skirt.
the ONE event that started the whole thing was the woman who chose to take the seat that should not have been taken if there were other options. And there were.