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It's true that trust systems are not moderated but when they use that power to tag someone in good faith
[like informing them of the existence of this thread] then that power should be revoked. Other than that I'm not urging the OP to do it, it's just a suggestion from me.

I am unsure that ever happened. Anybody who gets a negative tag for sending unsolicited PMs is probably deserving of it.
As for your proposal, you are free to do it yourself. You can send PMs to your friends or members you are close with, I don't believe anyone will tag you or report you to a moderator for that. However, sending mass PMs to a large number of random forum members with whom you have no previous contact is not recommended.
No, not always the one who sends an invitation to PM deserves a negative tag. I'll be more specific. Some time ago, an interview was conducted with forum users. Out of good intentions, the interview organizer sent personal invitations to everyone. And one day he got a negative tag from a DT member.
https://bitcointalk.org/index.php?action=trust;u=2654005The man felt he was being forced to take part. It took a while to change the review to neutral. Why bother once again people who are not ready to do something?
I also agree that this vote should be free participation. If someone does not want to write there, do not force him. Moreover, META is the central place of the forum, which most of the participants know about. And all the events there are unlikely to go unnoticed.