Yes I sat down at my degree ceremony, most embarrassing.
Years later the "direction" changed-
*** w02 9/15 p. 24 “Salvation Belongs to Jehovah” ***
"When national anthems are played, usually all a person has to do to show that he shares the sentiments of the song is to stand up. In such cases, Christians remain seated. If they are already standing when the national anthem is played, however, there is no need for them to take the special action of sitting down. It is not as though they had specifically chosen to stand for the anthem. On the other hand, if a group are expected to stand and sing, then merely standing up out of respect but not singing would not constitute sharing in the sentiments of the song."
Also in the 1960' and 70's (UK) it was customary to play the NA at the end of the last film at the cinema. Most JW's I knew would leave as the credits were coming up to save any embarrassment. One cinema I used to visit never played the NA but always played "A groovey kind of love". Never knew why!