I took Mat's lack of reaction to be a function of the place they were in and stress they were under - no extra energy or time to expend on being shocked, that sort of thing. It's clear Mat had no idea it was Jain from a subsequent PoV as was stated earlier.

 

I've often wondered what sort of things Ishamael did to him. For the record, I thought it was Jain as soon as RJ revealed his surname. I've thought any number of things that turned out not to be true, so I'm always proud when one does. :D

I agree. Mat only knew that this Noal is more than a simple, worn-out old fellow. Mat knew that there was something more to the man, but he did not know Noal is Farstrider,