What Already Exists, Partially

See folder README for orientation. It is worth being precise about what the sketch approximates and what is missing.

• Mastodon / fediverse (ActivityPub). Federation: yes. Status disregard: partial — likes and follower counts are still present. Algorithmic transparency: yes (chronological by default). Economic model: instance-funded, mostly unsustainable. Communicative-action affordances: no.
• Lobste.rs, Hacker News, smaller subreddits. Topic-centred: yes. Editorial gatekeeping: yes (sometimes accountable, often not). Communicative-action affordances: minimal (downvotes encode disagreement without obligation to engage).
• Substack, Ghost, individual blogs. Reader-funded economics: yes. Topic-centred: per publication. Public sphere as commons: no — these are publication-to-audience, not deliberation-among-participants.
• Kialo, Pol.is. Communicative-action affordances: directly. Kialo structures argumentation; Pol.is finds consensus across opinion clusters. Both are niche tools, not general platforms — possibly because they take Habermas’s medicine without the sweetener.
• Discourse (the forum software). Topic-centred, threaded, moderated, self-hosted by communities. Honest threaded deliberation. Modest in scale by design.

The pattern: pieces of the sketch exist. The integrated product does not. The integration would require taking adoption hits along several dimensions simultaneously.