Bond Air is so important...
The scene on the Bond Air flight in ASiB is SO important… It shapes Sherlock’s behavior toward John for at least the rest of Season 2, if not beyond.
Mycroft shamed Sherlock for showing off for Irene, except John was the actual focus of Sherlock’s showboating. Sherlock is profoundly embarrassed by his mistake and his brother’s poor opinion. He decides not to let it happen again--- to give up the obsessive love for John that created rash behaviors. No more ashtrays stolen for love. (There’s a reason they don’t giggle together after Bond Air like they did before).
Irene, as Sherlock’s mirror, learns the same lesson. Sherlock keeps her phone as a reminder that love is destructive, love hurts, love clouds judgment, love interferes with thinking.
John was sad that Sherlock wanted to keep Irene’s phone, but it’s infinitely more tragic than he realized because Sherlock didn’t care a bit about Irene. It was much worse than that. Sherlock was trying to forget John (romantically). He’s actively trying not to love him.
Despite his best intentions, however, Sherlock the romantic can’t quite follow through—not fully. Sherlock saves Irene (his mirror) at the last minute. He hasn’t given up on love completely. There is still a little part of himself that’s holding out hope. By saving Irene, Sherlock saves himself and will therefore continue to love John, despite his best intentions to go “cold turkey” in THoB.
Sherlock’s embarrassment over the Bond Air gaff and his subsequent attempt to “delete” his romantic feelings for John is the reason he poisons John in THoB and the reason he fakes his own death in TRF, leaving John clueless and grieving.