Some points of Botkin:

Since Kinbote isn't the King, he has to be somebody.  Everybody has to be somebody, right?  If his real name is Kinbote, what's his nationality?

Much of the fun of this "jolly romp" is seeing through Kinbote's deceptions.  His name is another one.  Nabokov called his real identity a "plum".

Botkin/Kinbote is yet another mirror reflection and lets Nabokov bring in the appropriate etymologies of both words.  And Botkin's transformation fits the theme of metamorphosis.

Having him be Russian lets him mention Russian words and talk about Russia, which Nabokov wants to do.

Botkin is one of the few surnames found in both Britain and Russia (up to alphabet), which is a blurring that fits with the theme of exile.  (Lukin is another, as some people here point out to support the possibility that Shade knew Russian.)

In particular, Victor Fet pointed out in April, 2007, that there's a Botkin Hollow and a Botkin Ridge near the border of Virginia and West Virginia, at about the latitude of Palermo.

http://listserv.ucsb.edu/lsv-cgi-bin/wa?A2=ind0704&L=nabokv-l&T=0&P=8406

In discussions involving Matt Roth and me, we found out that Botkin is a common surname around there, and that's where the diana and the atlantis occur near each other.  Maybe Nabokov chose that area for New Wye because of the Botkins.  Or maybe it was the other way around--he saw the name on a map, or on a storefront on some trip in the region, and recognized its bilingual potential.  I can even enjoy speculating that this was connected with the point in "An Evening of Russian Poetry" where the speaker says that once in West Virginia a Russian something came to him.

I too enjoyed the possible connection with the insane asylum in Moscow, so thanks to Ron Rosenbaum.

He says he doesn't find considerations of Kinbote's "reality" exciting.  Matt Roth asks whether we can know how reliable Kinbote is about events in New Wye and Cedarn.  I think there are contradictions and unverisimilar points in Kinbote's contributions--big trucks or not? did Kinbote write part of the commentary in the Wordsmith U. Library? did Shade really say, "Nay, sir"?--that tell us he's not reliable.  And I think that's exciting because it's our last undeception.  It reminds us that the unreal Shade is right in thinking someone playful created his world with its many thematic reflections, and suggests that someone playful may have created our world, in which Nabokov found so many thematic reflections.

(There, that's the shortest version of my reading I've come up with.)

Sun and star: For my best guess, physicists had known since 1957 (or earlier?) that carbon and all the heavier elements were synthesized (hm) in stars.  I can see Shade imagining how iron and carbon formed in ancient stars, drifted many light-years, became part of the material that the Earth formed from, and were made into his steel nail scissors.  The light of the sun, another star, now reflects dazzlingly from the scissors.  That's just the sort the sort of connection, cosmic and anti-climactically ordinary, that I think Shade likes.  I hadn't thought of Sam Gwynn's connection to the "moons" of the fingernails, but that would add to Shade's enjoyment.  So might the possible etymological connection between Latin "sidus" (stem "sider-", they tell me), star, and Greek "sideros", iron.

(Gary Lipon: The current consensus is that the plants and the sun coalesced separately from a single gas-and-dust cloud.

http://en.wikipedia.org/wiki/Nebular_hypothesis

However, at the time Pale Fire was written, that theory wasn't in favor, and I think some people did argue that the material of the planets had been part of the sun.)

If, however, the "sun" is a loop for a finger and the "star" is the hinge, I don't think that's necessarily a reference to the Russian riddle.

Jerry Friedman