I have an autistic son and he will often stand up during a flight or just gets stressed sitting near babys.
Several times we have prebooked seats for him and put noted on the system to sit in specific seats and BA normally accommodate him.

BUT sometimes they only sort this out at the airport so yes we sometimes throw people who have prebooked out of seats. In club we try and get him the window at the back so no one has to step over him and so he can get out. 64k is ideal, in CE we will go for row 1 so no-one is in front.

I am sorry if we have done this to you but he has needs we pay for club or first for him to avoid issues. So next time you see a someone who has thrown you out of a seat please don't blame them maybe there are hidden disabilities or other reasons they need to sit there.

thanks
JoeJet