Which has been broken with cw 3.10 refactoring. This also fix and incoherent
display pb in the regular cases: when adding first comment, it wasn't not
displayed similarly right after the ajax call and after a page reload.

actually make comment section 3.10 compatible: this div is now handled by the layout, no need for match_kwargs, no more 'Component' added to domid

avoid empty div when no comments and no right to add comment. Remove spurious parameters from ajax place holder url.

cleanup/refactor/document comment form generation on the way

fix comment's form handling: don't put comments relation in hidden section, simply use an HiddenInput. Also fix new comment detection