As it stands, as far as I know, the only benefit you get from training with someone is whatever IC information they decide to impart upon you. It's usually information regarding how a skill works, or what stats you should spend UE on, told from IC perspective.
Now, there's nothing wrong with this. It's a good thing that players should seek out other players in the same vocation to learn more about it. The point where I feel something is lacking, is when you OOC (and possibly IC) know how the skill works and what stats you should be getting. Because at that point, you have no real reason to train with another player and roleplay that out, even though an accomplished thief could learn a lot from a master thief. But it's very likely that the accomplished thief will gain nothing IC oor OOC from training with the master thief.
What I propose is a simple system to reward players mechanically for roleplaying training with other players. Perhaps a way to save logs of the last 10-20 emotes and say commands from both (or more) players involved. An admin reads over it to make sure no one's abusing the system, and clears it to award one extra UE a per day. Or week, if perhaps one a day might upset Sindome's slow progression too much.
I think something like this would prove a nice small incentive for players to share their knowledge, without upsetting the balance of progression or making people feel as if they need to train together to be strong.