You have a really quite patronizing view of passengers don't you? Displayed across multiple comments.
I sincerely hope you don't have a customer facing role.
Catch the 0009 Waterloo to Guildford on a friday or saturday night (or is that saturday or sunday morning?) and then you will have your answer!
Have you ever seen what happens when somebody tries to throw up out of an opening window?
It runs down the glass, gets into the heaters and smells delightful, oh this was at 2030 so not even late.
I used to make announcements on the lines of-
"if you were feeling unwell please use the bins provided instead of the floor or seat opposite", manglement found out and told me to stop.
Unless you have direct knowledge of the state late night trains get in I would recommend that you dont comment until you do because you have Rather an ideological view of them.