I'm spending a great deal of time with a colleague who has significant visual impairments and who, while a domain expert in their own areas, is neither particularly proficient with computer technology nor do they wish to be (there are certain prerogatives which come with age).
Hiding tools for compensating for poor accessibility design behind small, faint, hard-to-see, only-sometimes-visible, and/or other graphical elements is sheer madness.
Case in point: recent builds of Firefox have a "reader mode" feature, which I use heavily (my own visual capabilities are largely intact, but, well, 99.99966% of Web design is crap).
1. Is faint.
2. Appears at a corner of the navigation box. E.g., it's not at a Fitts point (top of screen, corner).
3. Worst and most unforgivably: it only appears AFTER a page has fully loaded, doesn't appear on all pages, and cannot be specified as a default (e.g., always open pages in Readability mode, unless broken).
From a UI/UX standpoint for someone who is already visually disabled this is unforgivable.
(Yes, I've submitted feedback to Mozilla on this.)