Here's how a basic quiet button looks like in Codex:
Button
That's it, it's just text, with no indication that it's interactive until you interact with it. I believe this goes against the accessibility principle of making our interfaces understandable for everyone (https://doc.wikimedia.org/codex/latest/style-guide/accessibility.html).
I am requesting that styling buttons this way be discouraged. Ideally, weight: 'quiet' would be treated like 'normal' if the button is not progressive, not destructive and has no icon. If that's not feasible, I'd appreciate a runtime warning, and if that's not feasible, then at least some discussion of the problem in the documentation (https://doc.wikimedia.org/codex/latest/components/demos/button.html).
It's not completely impossible to use this component in an acceptable way (e.g. a basic quiet button placed in a group with other kinds of buttons is probably understandable enough), but it is still always worse than any other kind of component (or even a plain non-Codex link).
Unfortunately buttons like that are not forbidden by WCAG (I found an interesting discussion of this at https://github.com/w3c/wcag/issues/800 and further links for in that thread, which I'd summarize as "it's not an accessibility issue, because it's equitably bad for everyone"), although they're touched on briefly in some sections of https://www.w3.org/WAI/WCAG21/Understanding/non-text-contrast.html:
Note that for people with cognitive disabilities it is recommended to delineate the boundary of controls to aid in the recognition of controls and therefore the completion of activities.
A button which has a distinguishing indicator such as position, text style, or context does not need a contrasting visual indicator to show that it is a button, although some users are likely to identify a button with an outline that meets contrast requirements more easily.





