I agree about messaging someone of any gender about work at night (without prior agreement), but why would it be wrong to smile at a coworker no matter who they are?
I disagree about messaging coworkers at night. I do it occasionally. Sometimes it's about something humorous, instructional or enlightening that I stumbled on while at home. Other times, it's serious and about work. I've had very productive and candid discussions with my CEO at 11pm. If I have something useful to share, I want to do it while I remember about it, instead of trying to remember the next day.
Thing is, when I randomly message someone at night, I don't expect a response, nor do I view my recipient unfavorably if they don't respond until morning or at all. Of course, it's different if the entire team is working late, but that's only happened a few times in the past 2 years I've been at my current company.
