Many questions on the site ask for explanations of specific commands, for TeX/LaTeX/Engine Foo. The informations is often directly available in one of canonical books like "TeX by Topic", "TeX for the Impatient", and of course "The TeXBook". At least some of these are freely and legally available as PDFs (assume for the moment that distribution issues were suitably settled).
It is technically quite simple to drop these PDFs on a website and provide an in-browser viewer for displaying them, also allowing anyone to link directly to a specific page of any hosted book. There may be existing services (Scribd, once upon a time?) to do this, and if not, Setting this up on github pages for example can be done with a couple of hours work. Knowing that the urls will work "forever", participants on the site could provide a directly viewable link to a precise location in a specific resource in comments and answers.
Implementation is easy, hosting is not a problem, assuming legal permission is obtainable or available, if there's no actual hinderance to putting this in place, would it be useful or useless? is it a good idea? would it have negative side-effects on answer quality?