Before revision: Until the user verifies the authenticity of the signature chain's root hash (or the keybase account) over an authenticated channel, the account and its associated identifiers are essentially blindly trusted, and the user is suspectible to a MITM attack.
After revision: Until the user verifies the authenticity of the signature chain's root hash (or the keybase account) over an authenticated channel, the account and its associated identifiers are essentially blindly trusted, and the user is susceptible to a MITM attack.