100% inappropriate if you know about the special circumstances I would agree, but not so much when those circumstances were not disclosed.

I volunteered for many years with both teenagers and adults with a variety of special needs, and it was often necessary to do a little preemptive ground work in some social settings, especially for those who presented no outwards clues to their particular needs.

A teenager who is apparently ignoring a FA trying to talk to them during meal service, preferring to keep their headphones on and probably avoiding eye contact, is going to elicit some sort of reaction from the FA.

Rather than condemn the FA for the way they handled it, wouldn't you agree from your experienced background that it would be better to realize up front that there would be no visual clues that the teenager in question needed special consideration and just quietly brief the FA in advance?

I think JDiver presents a very well thought out approach and going prepared with a simple card must make the interaction so much smoother, yet discreet for all concerned.