Drizzt did have sex with Vierna.
Bear with me here. First, Drizzt is an Unreliable Narrator: the story is framed as being his memoir, but he recounts events he could not possibly have known about, including the circumstances of his own birth and any number of other events he was not present for. Some things he might have heard about from others, and others are things he might have guessed at or pieced together from circumstantial evidence, but clearly there is some fair amount of speculation and even fiction in the story. Given that, why has Drizzt even bothered to include the references to Vierna's desire for him? Now consider the fact, referred to on the Fridge Logic page, that it really makes no sense for Drizzt to have concluded, entirely on his own, that there ought to be some sort of connection between sex and love. On one level, he is probably projecting backwards onto that earlier incident in his life the values that he picked up on the surface through his associations with humans and dwarves. Given all this, we must conclude that Drizzt's account of his graduation ceremony is inaccurate. What then, really happened? Why tell us about Vierna's attraction to him at all? It does not serve the story in any significant way. He could have left out that scene wherein he was confronted by Vierna when he was leaving the graduation ceremony altogether, or could have just written it as her telling him that he needed to go back in and take care of business. He certainly did not need to include the exchange between Malice and Vierna at his birth, where Malice warned Vierna "'He is your brother....When he grows older and those eyes pierce you so, remember, on your life, that he is your brother." It makes Vierna look like a pervert even by the standards of Drow society, when otherwise Drizzt makes clear that she was the least vile of his sisters. Maybe there really was something physical between Drizzt and his sister, but he cannot bring himself to publicly admit it in his memoir, but he cannot bring himself to completely ignore it either.- There's no actual confirmation that his sister was ever genuinely attracted to him. Malice accuses her of it...while he's a baby and she's fascinated by his eyes. Vierna never confirms it, even in her own thoughts, and her interest is easily explained by her actually possessing enough Goodness to feel an actual connection to her newborn sibling, unlike her sisters and mother Vierna was not completely heartless. The dialogue at the graduation makes it clear they were discussing him rejecting a completely different priestess (Vierna reacts with shock that he rejected a priestess and tries to drag him back in to make amends). Yes, her robe is open but drow do not have the same issues with nudity that humans do. The idea that she has incestuous feelings for him are merely the result of ambiguous wording and the misunderstandings by her sociopathic society for genuine sibling affection.
