“Tweet Marker” (https://tweetmarker.net) used to do this for Twitter (before their API became too hostile) and it was compatible with multiple great clients, across any device, with a simple API. It made keeping up with that site really nice, and I think it’s a feature worth considering for a social system we, the users, own! 💜
Cybrespace is an instance of Mastodon, a social network based on open web protocols and free, open-source software. It is decentralized like e-mail.