On Reddit, I tend to consider each top-level comment as “mini topics”. I find one interesting, and then I read as much as I can from it, which is limited by the usability of this interface. Which means I’m probably missing interesting comments because they were too deep, or inside a sub-branch I didn’t expand.
The difference between Reddit and Discourse is that whatever they are called, I rarely consider Reddit replies in higher esteem than mere “comments”. Rarely interesting, rarely more than a single sentence, rarely high-effort or value adding, and, of course, often dispensable (and riddled with trolls and bots).
On Discourse, or at least on meta (even if Discourse emphasizes this by philosophy), replies are much more substantial and deserve to be read.
Which makes the nested view, at least on meta, particularly unfit, if not incompatible.