1 Capt of a commercial/corporate aircraft flying in either capacity wears 4.
2 FO wears 2 or 3, depends on company protocol.
3 PPLs or non TRI/TRE instructors DO NOT WEAR ANY!!! (unless they want
to look real poser prats)
4 No-one, whatsoever, wears stripes on an overcoat unless they really
want to look a complete w@nker - it is very PPL. see 3 above. That is
just coming the big "I am!" to your oppos...which is saaad!
5 Crew positioning direct to/from a duty.
6 Some places it helps to impress bureautwats/minions at check-in etc
(at uncivilised airports.)