This sentence is nice sounding itsef, actually!
That made me laugh way too hard! :D
How does one say "fine", then? In English, while "fine" can mean "nice", there's also a flatter, "That's adequate" meaning. "That username is fine" "That username is acceptable."
That depends a bit on the circumstances, but I'd probably go with okej in most scenarios.
does this mean it's nice-looking/nice sounding?
Yes, exactly. :)
Sounding, but yes