Depends on how the person left. Sometimes it's clear that the Mets are willing to let a person walk. If they sign somewhere else, they get cheered the first time, then after that they're just another opposing player. deGrom's an example. Took more money than the Mets were willing to offer, and godspeed. When he pitches at Citi, he'll get a tribute video and cheered. If he's ever healthy enough to pitch at Citi, that is. If a player doesn't give the Mets a chance, bolts and talks shit on his way out the door, he gets booed. If it's somewhere in the middle, I lean toward not ever booing. It's a biznis, and players, agents and front offices do what they have to.