Actually I think you make a couple of great points that ought be
mentioned in the draft about implementability. (No chance you'd
have time to craft a paragraph? If not, I'll try pinch text from
above:-) Now that you point it out like that, I'm irritated at
myself for not having included it already! (It rings bells for me.)
OK, I think the place for a new paragraph is just before the last
paragraph of section 2. How about something along the lines of:
A complete and correct specification is not in and of itself a guarantee of
high quality implementations. What may seem like minor details can
increase implementation difficulty substantially, leading to implementations
that are fragile, contain unnecessary restrictions, or do not scale well.
Implementation experience has the potential to catch these problems before
the specification is finalized and becomes difficult to change.
You might also want to change the final paragraph of the section a bit in
light of the addition; I'll leave that to you to work out.
Hope this helps.
Ned