​​​​​​I recall my horrible experience coming back from BCN to LGW in 2014 on one of the old 737-400s. The original aircraft went tech in LGW and it took three hours for a replacement to reach us which then went tech and we spent a further hour sitting on the plane. The Iberia ground staff were hopeless as is generally the case IMO. However the crew were spot on, and the purser made sure that everyone knew their rights with regards to compo and made a detailed PA of how to claim it what to say etc.
In my line of work which is aviation ground Ops I make a habit of telling my family and friends if they’re delayed to claim for what they’re entitled, with regards to telling fellow pax I might tell the people I’m sitting next to if we were chatting which I tend not to anyway, but I wouldn’t work my way round the gate.