There are several ways to say "bye" in Syan, naal-kiaa is seen as "grumpy" or impolite since it is very neutral. Other options are:
Daala-mimin moa = if you won't see the person in a long time
Kadaa-moa = cheerful/friendly
Kasaa'daala = if you will never see the person again
Aad oliana-' = to announce you are leaving in a polite way
Aad kadaa-a = formal (to one person)
Aad kadaa-a o'moa = formal (to a group)
Aad kadaa-a o'akaado = to show respect (to a group)