Are there drawbacks to practicing Destruction on Ancano?

So, I was done playing for the night and decided to goof off a bit. So I saved and then went to blowup Ancano (in the college of Winterhold) because he bugs me.

I gave him both barrels of my Fire Spell and he just stood there. Shot him till he knelt down and then after a bit he came back up ready for more.

I did not think too much of it until I leveled up my Destruction skill by doing this.

So my question is... will anyone in Skyrim care? Is it just because this guy is a jerk that no one seems to mind that I flambé him? (Doubtful)

Or can you practice on any essential character with out fear of getting in trouble?

Update:

Here is a screen shot of me blasting him. If you look close, you can see that there is someone sitting in the background (by the window) and he does not care. (In case it matters, I am at the "Get the Staff" part of the Winterhold quest.)

I believe that you will still get a bounty if people see you attacking him i cant test this because i have finished the mage guild quest but im fairly sure you can attack him as much as you like he shouldn't be able to die he is integral to the mage guild story line the only 2 things i can think of are him fighting back and killing you or getting a bounty for attacking him.

Edit:

well that picture was funny, yes i believe you can attack him without problem, it might be a bit of a glitch because this is the first NPC i have seen that doesn't fight back when you attack him but from what i can tell it shouldn't harm you game in anyway to train on him. happy training!

he actually threw some lightning at me after about the 4th time I put him on his knee, but then not again for the next few times, and I got bored of it....