Overall seems like reasonable restructuring. I think this note feels out of place now though:
| * The cancel request code must not match any protocol version number |
|
* we're ever likely to use. This random choice should do.
I think it'd be better to remove that paragraph and maybe extend the section intro to be something like this (feel free to change/ignore as you see fit):
Reserved protocol version numbers. These don't denote an actual protocol version but instead have special semantics. These version numbers will never be used as an actual protocol version.
Finally, the newline addition at line 71 I don't understand the purpose of.
