These are ignored by Full-Text RSS at the moment, but we might add support for them in the future.
The site config files are also used by the popular Wallabag application, which does make use of those lines. Their users and developers contribute a lot of site config files to the repository, so that’s where they come from.
How would I do that?
(1) Login into my lwn.net account on my desktop browser.
(2) Exporting the session cookie.
(3) writing a custom lwn.net.txt config?
Yes, that looks right. Of course if the site expires the cookie you’ll have to do that again, but that’s one way to do it until we add support for login details or introduce some other way to handle sites that require a login.