When people say that the publication of HTML5 “blocked” by Larry Masinter’s “formal objection”, what exactly do they mean?

Why does the private w3c-archive mailing list exist? Why can’t anyone reveal what happens on there? What are the consequences for doing so? Who gets to be on that list in the first place?

Can anyone raise a “formal objection”?
Is anyone calling for the HTML Working Group to be “rechartered”? If so, what does that involve?
If there are concerns about the inclusion of Canvas 2D in the specification, why were these not resolved earlier?

Some background reading. I was planning to fill in answers as they arrive, but I screwed up the moderation of the comments and got flooded with detailed responses—I strongly recommend reading the comments.