Gnus Manual. Node: Choosing Variables
3.3.2: Choosing Variables
Some variables relevant for moving and selecting articles:
All the movement commands will try to go to the previous (or next)
article, even if that article isn't displayed in the Summary buffer if
this variable is non-
nil. Gnus will then fetch the article from
the server and display it in the article buffer.
This hook is called whenever an article is selected. By default it
exposes any threads hidden under the selected article.
This hook is called whenever an article is selected. It is intended to
be used for marking articles as read. The default value is
gnus-summary-mark-read-and-unread-as-read, and will change the
mark of almost any article you read to
only articles not affected by this function are ticked, dormant, and
expirable articles. If you'd instead like to just have unread articles
marked as read, you can use
instead. It will leave marks like
gnus-del-mark (and so on) alone.