Some time after finishing this quest, I went into the shop to sell some garbage items. When I tried to talk to the hume in the fancy dress, I got another cutscene. In it, the two other women behind the counter gossiped about Odasel's feelings towards Adelflete.
It seems like it was setting up for another part of the quest (or a different quest?), but I'm at a loss as to what the next step could be, if there even is one. Perhaps it could be related to why the diamonds are stackable, but I dunno... I'll have to farm some later.