tl;dr: Mozilla are removing RSS feed discovery and display features from Firefox in an upcoming release. This is an unfortunate decision which will actively harm the open web, and should be reversed. It is also part of a larger pattern of unfortunate decisions by browser makers which contribute to a user-hostile network.p1k3.com
I'm sad that RSS discovery was removed from prominence many years ago, but I totally buy their reasoning around Live Bookmarks. They never worked all that well, and the functionality should be put into an external competent RSS Reader instead -- like e.g. Mozilla's own Thunderbird.