Firstly, I’d make it an explicit rule that users must agree to.
i suppose, i doubt if that would accomplish much though.
Secondly, if someone gets caught doing so, warn them.
Thirdly, do it enough times (twice, thrice, whatever…) then ban them.
there is no way to “catch” them unless they admit to it. inconsistencies in content is no proof as to the cause.
as far as HIE, you’re right