We already allow public tampering, if you recall Deener's pitch to FAs media piece, that is allowable. Because all GMs can see it and weigh in with their own public pitches.

Heck the argument has even been (successfully! made that open chats (discords, groupmes, etc) are not really private if a lot of people have access to see what you are saying.

Tampering is going through other methods where others can't see you and trying to convince players currently under contract to jump ship and sign with you, or demand a trade to you, or whatever. That's just being shady and sneaky and undermining other GMs