A few notes that I'll put here because they're less specific and might be of interest.
1. I changed the wikipedia dakuten article just now -- it's rather misleading to suggest that dakuten were not used before Edo or suddenly spiked in use starting in Edo. Dakuten can be found in the earliest written Japanese, and the man'yogana distinguished between voiced and unvoiced syllables. They were used sporadically in most cases, and often written in a different color ink as if to set them apart from the "real" text. It was during the Edo period that you started to see the practice develop of using dakuten on all voiced syllables in a text, but I don't think it was universal until Meiji.
2. The "hiragana were inappropriate for men" is not completely accurate -- it was more that certain genres or styles of writing were used with one type of script. Generally the type of writing that was seen as more Chinese, foreign, educated, etc. was with katakana and things that were more associated with native Japanese was in hiragana. Waka, for instance, was almost always written in hiragana whether it was by men or women, and it was never considered inappropriate for men to write waka in hiragana.
The シ form in that manuscript is pretty standard from what I've seen -- if you see it close up it doesn't look as much like し. I actually prefer that way because sometimes it's really hard to tell the difference between ヲ and シ the way some writers write them.
