Rationalle: Comments need to be user-editable so that they can be posted
via git commit etc.
The _comment directive is still supported, for back-compat.
I think it is clearer to have one pagespec that controls all pages with
comments, and a separate pagespec that can be used to close new comments on
a subset of those pages.
Moved documentation out of contrib.
Mostly tweaked some wording. Moved documentation of various bits to other
pages (pagespec, etc), and linked to those.
Documented the new templates in wikitemplates.
Small quantities of documentation were removed. Particularly the list of
template variables, which I think is fairly obvious when editing the
template.