Discourse is also very wasteful of space for anything but long-form prose: a single line of text is 180px high (in other words, a typical screen will never under any circumstances fit more than five comments on the screen at a time), and a single-line quote from someone else adds 80px. Compare discussions here on HN with Discourse. I’d much, much rather work here. (Yes, their purposes are somewhat different, especially as regards ordering; and applying the HN structure to longer-term discussion would require changes of some form, because it wouldn’t work if you just took it verbatim.)
If I had infinite time, I’d write a leaner frontend for Discourse with much less magic and much less wasted space.