Some info about users that are silenced:
Silence reasons are not public but suspension reasons are.
As for why they are public I dont think it was ever said here but when suspetions were first added to Stack Exchange when Jeff Atwood still worked there (he made the blog post iirc) saying its a durtrent for other users since its something they can see moderators take actions.
As for the site I mod most reports we get are not spam. If we arent sure we check their profile mainsite (its a forum for a compeny so we have SSO) and see if we have anything there. If we are still unsure we allow and action if needed later.