> So Sidebar is perhaps a kind of block-linked-to-document rather
> than block-linked-to-point, perhaps something else.
Ping! Sorry, but you pushed a button there. Conceptually, a sidebar is
basically a footnote that gets printed in the margin. I see no reason
to treat it any other way than as a special case of <footnote>, with
positional _recommendations_ in an attribute.
///Peter