안녕히 계세요 is said as you are leaving: stay where you are in peace.
안녕히 가세요 is said as someone else is leaving: go in peace.
If both people leave, I suppose they can say 안녕히 가세요 to each other, right?
That would be 안녕히 계세요, no?
Thanks. I fixed it. The Korean course might have been altered since I last commented.
@duolingo: since you do not mention who is talking/in which position, and since 안녕히가세요 does mean good bye... WHY IS IT CONSIDERED WRONG?
Ehh I'm Korean and I still get some of the questions wrong...the grammar is pretty bad