I had the „pleasure“ once being advised by a colleague in the cabin from another airline and rated for a different type that we were not allowed to take off as we had cold soaked fuel frost on the wings, while already being cleared for takeoff. After a short chat with the Senior Cabin Crew and on her advise, we taxied back de iced, right at the runway of course and with engines running, and went on our way. After the flight we asked him into the flight deck and kindly explained that cold soaked fuel frost in certain limits (black lines on the wing) is actually allowed on this type.
Knowing a little can both be costly and ultimately dangerous.