* lisp/ox.el (org-export-filters-alist): Remove reference to comment
filters.
(org-export-filter-comment-functions,
org-export-filter-comment-block-functions): Remove variables.
* doc/org.texi (Advanced configuration): Remove reference to comment
filters.
* etc/ORG-NEWS: Signal removal.
Comments are removed before parsing the buffer. As a consequence,
filters are never called.