I don't see it as a hostile work environment at all. People can message me whenever is convenient for them and I'll read and respond whenever it's convenient for me.

I work with people from different time zones and people who like to keep different schedules, some waking up very early or working very late, and I myself wake up pretty late. It just doesn't make sense that I should demand people message according to my schedule, but I'm also not going to wake up early or work late to match theirs.