[quote=@Burthstone]
<Snipped quote by Silver Fox>

Simple: He doesn't have bruises and such. Real-Karn got the hell kicked out of him back at the council, and I'm pretty sure he hasn't fully recovered yet, nor had any way to. And fake reactions to pain are hard to do.
[/quote]

Actually, they do have bruises. I just forgot to specify. Just said they were a perfect copy, but never said they were perfectly healthy looking xD 

But both will fake "I'm fine!" It xD

But I do agree with your second point. Isn't soooo easy.

But again, none of them know Karn very well. So it be a little weird if they caught on with those little facts.