I appreciate the difference between a phobia and an aversion. I agree that a superstition may be trivial and without noticeable effect. I am equally aware that it may have a serious effect on day-to-day decision making.
It does seem that N had a number of minor peculiarities, which as has been pointed out, may mean very little. On the other hand, if the obsession with open doors is true, then that suggests something rather more unusual than the fairly common dislike of cats.
Barnett makes reference to the open door obsession on p165 of the Wordsworth edition of Bonaparte. He gives the source as Le Normande, MA. Historical and Secret Memoirs of the Empress Josephine. 2 Vols London 1895. See Vol 2, pages 40 and 293. Barnett mentions several other strongly held superstitions as well.
When it was pointed out that he had lost 500,000 men in Russia, N commented "What are half a million men to a man such as me?".
Hmmm. Cue Digby Smith