Out of respect to the people who put a lot of effort into what questionnaire has become, I would like to correct a few of your points.
To begin with, I respect the decision that was made to include Feedback into core. A decision had to be made, and at the time, the noise that was coming from the community seemed to tip the scale toward Feedback.
The reality of questionnaire is that the entire module had been rewritten to make the interface what the people wanted before Feedback was announced as a core module. It was released into contrib almost the same week as the announcement. Communication was just not what it should have been to give Moodle the information they needed to know that.
Now to specifics:
I do not believe this is the case. Joseph dedicated a lot of time over the last years to resolve these. There are no hard-coded styles that I'm aware of (there are some unused constants that have been removed just recently). There are some tables in some of the question formats, as there are in Feedback.
all the questiontypes being crammed into one file instead of being pluggable
Somewhat true. Making them pluggable was being held off while it was determined if the question library could somehow be used instead. Feedback does have somewhat pluggable questions, but does not use the question library either.
no inline documentation
Not true at all. There is a ton of inline documentation. One of Joseph's biggest efforts was in this area. And it has translations into many language packs.
and needs quite a bit work to review it properly and polish it up for 2.0
Not sure about this either. A version already exists in 2.0 and is being constantly updated with the changes to 2.0.
Questionnaire has a very large install base, and will continue to be maintained and improved. At some point down the road, when Feedback satisfies all Questionnaire users, it might be possible to create a migration path from one to the other, allowing the two projects to fuse.
Mike