In my understanding, Firefox Reader Mode (and similar features in other browsers) reads in the entire page and, based on analyzing the page for cues, then decides to offer the user an option to choose reader view (or not).

So while it helps improve readability, it doesn't cut down the time to load, the amount of data downloaded, and probably helps improve the battery life only marginally (this is debatable, depending on the amount of active JS, auto-play videos and also at what time offset t the user chooses reader mode after the page loads).

The impression i have of this reader mode is that it relies, in part, on pages offering markers for printing.

I have in the past noticed that reader mode will not be available of i have killed the JS on a site that enable their print format.

Is that a "community" effort? or a Mozilla effort?

Mozilla is a community effort.

Fair enough. I guess I my question is: FF is a funded community effort. Is there a non-funded community effort?