It's a really big part of elven lore, actually. It's also one of the driving reasons Vhaerauns regularly bring on surface elves - breeding with them has every much chance of producing an elf as it has a drow. So they'll either have more surface elves to bring under their thumb or properly increase their numbers with another drow. It's win-win, really! When it comes to drow/elf children, think of drow as being the dominant gene.

Though, I do recall hearing once that silvery hair is looked down on in Lolthite society, because silvery hair is supposed to be a sign of impure (read: surface elves) bloodline.

I don't know of an explicit source, Iron, but I've always just assumed it logically. If the offspring of two different elven subraces (for example) was a half-breed and not fully an example of one subrace or the other, then subraces would have long ago been significantly or even completely bred out of the race.

I didn't mean to argue that a child born of a union netween two different subraces couldn't carry over a subtle trait or two from the parent of the other subrace, Iron. Just that the the child is, in every mechanical and societal way, considered to be fully a member of one subrace or the other. She's not half-'n-half.

All noble backgrounds require approval. Underdark drow houses are the only exception. Afaik.

It's specifically noted in several sourcebooks that elven subraces breed true, not into half-breeds of one or the other. Complete Book of Elves is the most obvious place I can think of.

This is canon lore we use for the server. Note that minor things carrying over (like eye colour of one of their parents or something like that) is fine, in my opinion.

Suspicion and in-character persecution aren't evidence of a lore exception to the general rule. While it has little actual impact to play as the character will believe what is plausible to the character, it is important to note it is just a witch hunt.