Is this against any Nostalrius rules?

So, I just saw a 34 mage grinding away in the Yeti cave in Hillsbrad.
Up and down just killing Yetis over and over. Apparently grinding away for xp.
Nothing strange about that. But...
He had a lvl 32 warrior from the same guild on follow all of this time.
The warrior never did anything and never deviated from following the mage.
So basically this guy was grinding xp for not only himself, but for another player too at the same time.
When I confronted him about it, he said that it was all according to the Nostalrius rules to do it this way, and that the other character was his gf's (who was taking a nap apparently).
So my question is: Is this legit? Can I party up with someone, set follow on him, tab out and watch a movie while he grind xp for both of us? Thats not playing for yourself. I personally dont see any difference wheter you are using a bot to do the leveling for you, paying a chinese to powerlevel you, or having a friend do it while playing his own character. In each of this scenarios the bottom line is that you gain levels without actually doing anything yourself...
Up and down just killing Yetis over and over. Apparently grinding away for xp.
Nothing strange about that. But...
He had a lvl 32 warrior from the same guild on follow all of this time.
The warrior never did anything and never deviated from following the mage.
So basically this guy was grinding xp for not only himself, but for another player too at the same time.
When I confronted him about it, he said that it was all according to the Nostalrius rules to do it this way, and that the other character was his gf's (who was taking a nap apparently).
So my question is: Is this legit? Can I party up with someone, set follow on him, tab out and watch a movie while he grind xp for both of us? Thats not playing for yourself. I personally dont see any difference wheter you are using a bot to do the leveling for you, paying a chinese to powerlevel you, or having a friend do it while playing his own character. In each of this scenarios the bottom line is that you gain levels without actually doing anything yourself...