I doubt tthere's enough cannon information to answer that question.
We have the fact that Kellhus' children look like him, I think, which is strange considering what would be a host of recessive traits IRL (Blond hair, blue eyes, etc.).
We also have the Scylvendi legends of women being killed for having blond haired children, which again is strange given what I assume is their typical genetic heritage - you wouldn't assume that blonde hair would show up at all.
Can't think of much else - not a lot of evidence really.
I don't even know we should count the children of Dûnyain fathers for that, because they seem to have their own specific super-dominant genetics at work. I would assume that the children of a non-Dûnyain Norsirai man and a Ketyai woman would
not look like the children of Kellhus and Esmenet, for the most part. Sure, there would be a slightly possibility of blond hair and/or blue eyes appearing in one or two of the children, depending on what recessives the mother might have (just look at green-eyed Mimara, for instance). Aside from that, I have a hard time believing children of mixed Norsirai/Ketyai ethnicity wouldn't be
mostly black-haired, brown-eyed and dark-skinned (though lighter-skinned than full-blooded Ketyai people).
That was just the case of Cnaiür's mother, if I remember correctly...were there others? You are right in that it would be strange that blond hair would appear at all among the apparently highly homogenous (from a genetic standpoint) black-haired Scylvendi population. But there is - once again - the involvement of Dûnyain genetics in this case, so we can't conclude anything from that. (Dûnyain could probably have children with Satyothi women that would come out blond, blue-eyed and pale-skinned, as completely genetically implausible as that sounds.)
Scylvendi do tend to capture Norsirai women from time to time, right? So I think there could be
some genes for blond hair around, but definitely not widespread (this is probably the case with
Anissi, for instance). We do know of a(nother) person of mixed Scylvendi/Norsirai ethnicity (Moënghus II) that strongly favours the Scylvendi side (but again, one case, can't conclude anything).
One of these days I have to make a thread listing the appearances of all available characters compared to their parents (Dûnyain and part-Dûnyain excluded) to see if there really is anything there.
Probably. Humans are spectacular at pattern recognition. Seems very likely that though he might otherwise be normal looking, or even beautiful given the Nonmen general physique, I'm sure people would see an 'otherness' in his appearance. This could be a turn on, rather than a turn off, though - making people drawn to him rather than the reverse.
I can see that being the case, Sanna-Jephera having a kind of strange beauty, with more chiseled features than regular humans and the like. Maybe he would have paler skin than the average Norsirai, too.
Cimoira, on the other hand, might have had slightly softer and more rounded features than the average Cûnuroi (but not
too noticeable), maybe slightly larger eyes too.
(And this just gets me thinking that we need fanart of these two...)
Insufficient data
Exactly.
Besides, what does Bakker even know
.
Now, now, Wilshire, I'm not saying anything against Bakker by any means.

What he said in that AMA seemed to be the general rule among Nonmen anyway, Gin'yursis seemed to be in the minority there (assuming, of course, that part of the legends is true).