I could never really follow the “multiple personality” theory espoused by C. Kunin, Roth and others, although I have the recurrent feeling that the three main characters are “one.”  I wish I had access to Couturier’s arguments about the Author’s presence as another character in PF because it might offer a thread into the “three in one” project.

This complication is well expressed by SE Sweeney in “Playing Nabokov”:

“Look at the Harlequins! not only smacks of “autoplagiarism.” It takes the game of playing Nabokov to new lengths, as when Vadim tries to remember his last name:
I definitely felt my family name began with an N and bore an odious resemblance to the surname or pseudonym of a presumably notorious (Notorov? No) Bulgarian, or Babylonian, or, maybe, Betelguesian writer with whom scatterbrained émigrés from some other galaxy constantly confused me; but whether it was something on the lines of Nebesnyy or Nabedrin or Nablidze (Nablidze? Funny) I simply could not tell. I preferred not to overtax my willpower (go away, Naborcroft) and so gave up trying. (210-11)3
Indeed, many readers cite the novel as proof of Nabokov’s narcissism [   ] Yet I think that these readers miss the point. Although Nabokov stresses Vadim’s resemblance, he also denies their identification. “People tend to underestimate the power of my imagination and my capacity of evolving serial selves in my writing,” he complains in Strong Opinions ... Accordingly, Vadim is calculated to make a fool of anyone who reads the novel as a roman à clef. [  ]Appearances are deceiving, however. Dean Flower’s comment on Nabokov’s notoriously contrived interviews seems appropriate here: “the point of these fictions is not so much that [he] must conceal his private life … as that he expresses himself better by adopting a persona” (148). Look at the Harlequins! is thus an ingenious answer to charges of autoplagiarism and narcissism, and an inspired resolution to the conflict between man and fictionist. If Vadim is analogous to Nabokov, then the fictitiousness of his apparent reality suggests that the reality Nabokov shares with his reader may be equally elusive. “Playing Nabokov” is, after all, only a game. » (http://revel.unice.fr/cycnos/?id=1295)

Although it’s easy to understand the meaning of “serial monogamy,” what VN means by “serial selves” still eludes me, although it helps me to look at Pale Fire as a grand play in which different ego-parts are projected ‘outside’ by their ‘host,’ but without achieving a definite independent life(which would  result from an actual splitting of the host into different personalities who ignore one another’s existence.) For example, if we could admit that “N” represents both Nabokov’s “presence” and the chess “Knight” and/or the fairy chess “Nightrider,” all the associations related to the double-meaning of “fairy” and of Kinbote’s (a parasite, a bot-fly…) flamboyant usurpation of a throne and Shade’s poem, would implicate at least one of “N”s personae, without demanding a “split.”

Btw: What is an “iridule”? An illusion that represents a distantly staged reality or “a mirror of exile”: “The iridule — when, beautiful and strange,/In a bright sky above a mountain range/ One opal cloudlet in an oval form/ Reflects the rainbow of a thunderstorm.” (connection to alder: “Line 109: iridule [  ]  An iridescent cloudlet, Zemblan muderperlwelk. The term "iridule" is, I believe, Shade’s own invention. Above it, in the Fair Copy (card 9, July 4) he has written in pencil "peacock-herl." The peacock-herl is the body of a certain sort of artificial fly also called "alder." So the owner of this motor court, an ardent fisherman, tells me. (See also the "strange nacreous gleams" in line 634.*)
^{* 633-4}   “And dealt with childhood memories of strange/ Nacreous gleams beyond the adults’ range.”

The Erlkönig poem offers a promising scenery for the conflicting self-parts (of Kinbote/ “N”), comprising the father who tries to protect his little boy (JS), the frightened child (N) and the menacing enchanter in their pursuit (K/N). With this hypothesis in mind, it might be worth reading afresh some of the entries related to “alderkings”:

Line 275: [   ] “As in the case of some of his predecessors, rough alderkings who burned for boys, the clergy blandly ignored our young bachelor’s pagan habits, but wanted him to do what an earlier and even more reluctant Charles had done: take a night off and lawfully engender an heir.
[  ]  On the eve of his wedding he prayed most of the night locked up all alone in the cold vastness of the Onhava cathedral. Smug alderkings looked at him from the ruby-and-amethyst windows. Never had he so fervently asked God for guidance and strength (see further my note to lines 433-434). //After line 274 there is a false start in the draft: “I like my name: Shade, Ombre, almost "man"/In Spanish...” One regrets that the poet did not pursue this theme — and spare his reader the embarrassing intimacies that follow.”

Line 662: “Who rides so late in the night and the wind: This line, and indeed the whole passage (lines 653-664), allude to the well-known poem by Goethe about the erlking, hoary enchanter of the elf-haunted alderwood, who falls in love with the delicate little boy of a belated traveler.[  ] Another fabulous ruler, the last king of Zembla, kept repeating these haunting lines to himself both in Zemblan and German, as a chance accompaniment of drumming fatigue and anxiety, while he climbed through the bracken belt of the dark mountains he had to traverse in his bid for freedom.”

Line 894: Shade: "True, sir. In due time history will have denounced everybody. The King may be dead, or he may be as much alive as you and Kinbote, but let us respect facts[  ] "Strange, strange," said the German visitor, who by some quirk of alderwood ancestry had been alone to catch the eerie note that had throbbed by and was gone.// Shade [smiling and massaging my knee]: "Kings do not die — they only disappear, eh, Charles?" [  ] "Didn’t you tell me, Charles, that kinbote means regicide in your language?" asked my dear Shade./ "Yes, a king’s destroyer," I said (longing to explain that a king who sinks his identity in the mirror of exile is in a sense just that).”

The strength of John Shade’s “Pale Fire” to stand by itself would then represent the poet’s victory over his various phantoms.