Teaching magic spells through weapons

Yes, the post was to you, Halo.

The game's events do not remove equipped espers from any party members at any time before you gain your first set of espers in zozo. Suppose you give banon the Ramuh esper, and you forget to remove the esper before he leaves the party. When he is removed from your party, the esper will go with him, and you'll never get it back.