I had recently logged on with my thief for about 5 mins at most, and all I did was look at the Galadon thieves guild bartender a few times (peek) and type list a few times. (I also wandered around town looking at the healers cuz I was bored.) I didnt buy anything (Im pretty sure) and when I logged out I got 85 commerce exp. points. Not sure if this is a bug, or if I can spam list or look and get tons of XP or what..

Gaining commerce xp is typically delayed. You probably earned that xp on your previous login.