Late to the party, but I had two encounters earlier this year:

Back in April, I boarded UA's early morning RNO-SFO right behind FoundInRNO, who had his tag prominently displayed. Turned out we were across the aisle from each other. In June, bobes spotted my tag as we waited to reboard a mechanically-delayed UA flight IAD-SFO after it had returned to IAD.

Also recently had a lurker say hi at the SFO CO Presidents Club.