Ulysses - Man in the Macintosh

He's the 13th mourner at Dignam's funeral, and is mentioned a few more times through the day.
Nabokov thought that it was Joyce inserting himself in his own book, but there are two other possibilities that seem worth mentioning: Mrs Sinico's widower (from "A Painful Case") or James Clarence Mangan. Interesting. I prefer Nabokov's opinion, but there's a distinct possibility (given the source) that it was tongue-in-cheek, or N. was just playing devil's advocate, or provoking someone else who put forth a really odd idea...

The Captain Sinico hypothesis I find rather odd, to be honest - there doesn't seem to be anything in the story itself that would suggest it - not that there's much in Ulysses that gives away who the man is... Perhaps it's the lingering image of a man alone that suggests it.

The Mangan hypothesis is perhaps more convincing, but no more so than the idea of Macintosh being Joyce himself, if not for my suspicion that J wouldn't tarnish the book by putting himself in there, no matter that he'd put everything around him into the book.
Mangan: a poet, translator and essayist, well connected with the Young Ireland movement... Something of a tragic figure, he apparently was "a lonely and difficult man who suffered from mood swings, depression and irrational fears, and became a heavy drinker. His appearance was eccentric, and later in life he was often seen wearing a long cloak, green spectacles and a blond wig." So the long cloak thing was well enough known, and he died fifty or sixty years before Joyce wrote the book, so the timing's right... It'd be interesting to trawl through Joyce's letters and diaries, to see if he mentioned Mangan, and in which circumstances.