Grishka wrote: The fourth note said to have been erased is a) not visible at all, and b) harmonically wrong, inconsistent with the rest of the song.

Be careful with this. Looking at photographs of MSS. can often give wrong impressions. You've likely heard of palimpsests -- overwritten manuscripts. There were techniques for erasing inaccurate texts -- with a knife, with chemicals, by overlaying with another ink. Usually scribes didn't do this; they just put a line of dots to mark a deletion. But in a musical setting, that might not work. Such an erasure might be visible to the eye (e.g. by moving one's head about) when it is not visible in a photograph -- or it might be felt with the hand, or it might be detected by infrared or ultraviolet photography.

I'm not saying that is the case in this particular instance; I've read up quite a bit on the Harley MS., but it has been a while. But this is an important general caution. Looking at a photograph of a manuscript is no substitute for seeing a manuscript. Believe me, this has tripped people up badly.

(Of course, it cuts both ways. Just being in the presence of a manuscript is no substitute for a full set of photographs in five or six colors. I seem to recall one MS. that was photographed in something like eight colors -- red, green, blue, white, IR, UV, and some intermediate shades -- that turned up all sorts of interesting things. And, of course, there are also X-ray photographs, which can sometimes reveal things that have been painted over -- that happened with a portrait of Richard III, e.g. It had been repainted to make him look worse.)