Following up from faster junk mail deletion with mu4e, elfeed is another candidate for enabling actions on pages. In this case, marking rss entries as read, page by Page.
If on use-package, the function can defined and bound to the "v" key using:
(use-package elfeed
:ensure t
:bind (:map elfeed-search-mode-map
("v" . ar/elfeed-mark-visible-as-read))
:config
(defun ar/elfeed-mark-visible-as-read ()
(interactive)
(require 'window-end-visible)
(set-mark (window-start))
(goto-char (window-end-visible))
(activate-mark)
(elfeed-search-untag-all-unread)
(elfeed-search-update--force)
(deactivate-mark)
(goto-char (window-start))))