Maybe it's a spectrum from low to high [trust?] based on how many common people you and I interact with and how frequently we interact with them. Also based on whether we have frequent and direct interactions with each other (DMs, comments). On the user side, we wouldn't have to do anything. It could just be a calculated data point represented visually for users to see on each other's profiles.
This might be the only realistic way to do it. Twitter had a show less option and maybe that was their wot.
That might have fed to their content algorithm and used as an input to show us a more relevant feed (eg show less people talking about diet and politics). I thought this would be more of an indication for users to quickly view whether this person is a bot or untrustworthy scammer. Have you heard of hive.one back when it was up and running? It was ranking twitter profiles within a group/community we belonged to based on common relationships. Might be interesting to see which data points they were pulling.