Is there any HTML that can be wrapped around the spacer-indents that would mark them as indented for screenreaders? If I knew more about this I’d propose that as a unified diff, so that they could apply it to their templates and solve this, but I don’t :(
(I know there’s ways to restructure it completely to do this, but I like focused and surgical changes that don’t affect anyone who doesn’t notice them. Opinions vary on that.)
For screen readers, there's the "tree" aria role[0] which lets you mark a specific element as a tree, and mark the elements within it as items at a certain level.
Tree wont' be a good fit for comments because one would want to read content by line/word/etc. while a tree item is presented as a whole thing by the screen reader so it's only good for small textual items.
(I know there’s ways to restructure it completely to do this, but I like focused and surgical changes that don’t affect anyone who doesn’t notice them. Opinions vary on that.)