agenda+ HTML Ruby Extensions review

I'd like to review the pending comments at
https://github.com/w3c/i18n-activity/issues?q=is%3Aissue+is%3Aopen+label%3As%3Ahtml-ruby-extensions

Btw, note that i added to or edited several of these issues after the 
initial commit, so you should read them on GH, rather than in the email 
notifications.

ri