The character listing on this site lists all the fades before LOC (when Shaidar Haran is introduced) who smile under Shaidar Haran, because of Alviarin's quote that "Fades never smile. Never." (when she was marked by SH in COT)

 

Except for one. In SR, in the first trolloc attack in the waste by Mat's POV, he almost is killed by a fade who grins as he says "Time to die Hornsounder" (or something like that). His aiel buddies save him and kill the fade.

 

What do you think? Could SH be more powerful than we thought, is Alviarin mistaken, or am I just making a big deal out of a minor error?

I don't think there was any error. I know Shaidar haran is quite obviously different than any any other Fade, So much so that I don't think he equates as a Fade but i have noticed that in certain Battles done one-on-one there have been times when the Fade did exhibit characteristics beyond the norm such as the smile.

It may be tahat the grin is not as much a movement of the face or and expression, it may just be a feeling that is given of a feeling of joy?

Well, technically a grin could be different than a smile. It could be more of a fierce grin, like a snarl. Or we might be making a big deal out of nothing idk :D