Grishka wrote:

All the other erasures remain unexplained as well, unless there is more recent research. If the MS is examined more thoroughly physically, we may get answers to some of our questions. Who knows of such research?

Unfortunately, based on what I've heard, new research may be hard. The British Library sometimes withholds certain items from examination because the demand is so high and there is so much wear and tear. And Harley 978, as I recall, is one such manuscript. (I can't remember my source, so I could be wrong.)

It's not just some really old manuscripts that get that treatment, by the way. One volume of the diaries of Charles Dodgson -- "Lewis Carroll" -- is also withheld, because that's the one that originally contained the page describing how he lost his contact with Alice Liddell and his sisters, and that page was cut out by someone, probably one of his family. Everyone wants to look at that missing page, so the book went on a very restricted list lest it be damaged.

I'll mention again that one suggested reason for the explanation is that the scribe was composing as he went along. Of course, that wouldn't explain why the notation was being corrected. But maybe the scribe was still getting used to the new notation. (Which probably argues for the earlier date for the MS.)

Part of the problem here is that people are pushing paleography too hard. Often the +/- on a manuscript is on the order of 150 years! And here they're trying to date Harley 978 to within +/- 15. Paleography by itself can never date a book that precisely.