I always have good nights and bye is used..goodbye
Because we all live in so many different time zones, LOL! The one next to you it's surely a good night! Don't say 'goodbye', say 'see u again tomorrow'! LOL!
"Good night" might too closely match "good evening".
EP admin wouldn't put "good-bye" because they never want us to sign off!
I guess it's a cultural thing. I've known people who use them interchangeably. As in, "I bid you good evening." as they are exiting. :)