Used to drive the Scotland - LHR and North England - LHR flights for a well known UK carrier and if I saw cabin crew in uniform getting on I would always ask my No 1 to upgrade them if space was available. Most staff dont give a monkeysabout the C class meal but dont enjoy the wise cardks from the the Y pax. Once you ahave heard it once etc.
Equally, if I saw astaff member I knew travelling in civvies I would always make a point of going back in to cabin to speak to them and their family / partners before depature and offering flt deck seat / visit and apologising if we couldnt upgrade them. We all play to the same hymn sheet, so why not be pleasant to each other ?