Reddit's reputation system gives new arrivals equal weight to long-standing highly trusted members of the community, and does not include priors about content quality based on poster's history. It's the simplest thing which could barely work, and does not allow for high quality discussion to scale without relying heavily on moderators or other social things not present in all communities and not able to resist certain forms of attack. It also lacks adequate indexing and browsing by topic, making discussions temporary rather than able to produce lasting artifacts and be continued easily.
SE's reputation system is a little better (you need to prove to the system you can productively engage with the topic before your votes have any weight), but it's very focused on QA, which is not a great format for extended truth-seeking discussion.
Cool argument structuring seems like an optional bonus (still great to have, but not necessary for the thing to work), but features that give users reason to expect their high-quality content gets more eyeballs (particularly the eyeballs which most need that specific content) seem core and essential.