Design matters! Thanks for laying this out for people.

Would be great if you also did an explainer piece on another primary difference - Mastodon is FOSS and is not any kind of business/company. Twitter is a closed/proprietary corporate platform.

Mastodon came from people wanting some particular type of tool/platform and creating it that way. There's no 'business model' in the mainstream sense. The design of mastodon is what it is because its originators wanted it that way, and money was never a factor.

Twitter is about making money for its shareholders. Ads have been (up to now anyhow) their primary source of revenue. As with all profit-centric media, it's about drawing mass quantities of eyeballs (or eardrums, back in the radio days) to ads. Virality is a fantastic tool for that. Which is why it's the foundational element of Twitter and all the other corporate platforms. The design has to endlessly create new waves of mass attention for advertising.