Man, lots of the takes were very, very off.
Twitter is actually quite onside in its choices to flag and fact-check tweets.
The platform can flag the content to its heart's content.
1. Realtime/advance knowledge of all content
2. Opportunity to exercise editorial control on it.
3. Ability to do so.
Clearly every social media platform admin fails 1 & 3 at least.
This dismisses the argument put forward by some, myself ignorantly included, that if Twitter fact-checks Trump but not others, they've automatically failed to meet the test. Partial ability to curate content in fact PROVES they qualify.
But of course, this implies strong fact checking ability growing alongside, which is already happening with advances in data journalism, semantic web, and NLP.