As requested, APA reviewed the CSS Multi-column Layout module Level 1 (https://www.w3.org/TR/css-multicol-1/).
APA agrees with the concerns Rachel brought forth at w3c/a11y-request#2 and has nothing more to add to those concerns.

However, APA does request an Accessibility Considerations section be added, which acknowledges potential issues and references WCAG. Statement could read:

"Setting container height and line length can pose challenges for people with visual or cognitive disabilities. See WCAG Success Criterion 1.4.10 Reflow and
WCAG 1.4.8 Visual Presentation to understand user needs."

At the end of Section 2 of the spec, a note is already present about accessibility issues occurring if the column's height exceeds the viewport height. Adding a page anchor at this point to lead down to the new
Accessibility Concerns section would likely be helpful to folks exploring the spec. It could read:

"See Accessibility Concerns for additional details."