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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.