Dear Andrew,
Since Dmitri is the source, perhaps we should wait to hear what he has to say on the subject? Personally, when I claim that an idea is absurd, I am in fact ridiculing it. We are speaking here of an argument among academics not Godot, after all.
And while many share your dismissive attitude toward the Stevenson story, Nabokov was not one of them (see his Lectures on Literature). By the way, have you read it? It is hardly simple, there are multiple narrators, its form is more complex than Pale Fire and the prose is sometimes aped by Nabokov's own.
Carolyn