I don't think they did know what we meant by initials; they were clutching at straws by that point. They might not have agreed if they knew it entailed the kind of run in & break that has tower controllers spilling their coffee down their shirt
They collared the other pilot on landing with "Do you do that at home?" to receive the response "Lower usually, I'm the Display Pilot"
p.s. I recall the -71 story was FL600, as IIRC FL660+ is uncontrolled airspace - one knows these things 
p.p.s. My first ever flight was with my dad from Panshanger, aged 3, in an Auster. Some boys never grow up!