I think the privacy risk is more prominent when you don't know that information is being made public. A system like this would obviously tell users that their upvotes are counted towards the trust system and therefore people would upvote based on that. I guess we could make it all hidden, similar to Youtube's algorythm where the trust graph is not publically available and only works in the backgrounds to change the upvotes you see for the people you trust (so it changes the upvotes but you don't see how it changes and other people can't see yours), but I believe that would be more concerning and likely to be abused then if the information is always available for everyone.

As for the gatekeeping and groupthink, I think that already happens regardlessly of a trust system, and is a consequence of tribalism in the real world rather than the cause of it. Honestly, I see it beneficial that people who despise each other get more separated, and usually it's the forceful interaction between opposing groups that results in violent outcomes.