Per this, I think it would be nice if when someone edits their message to quote or tag another user, it still sends them an alert as if you had quoted or tagged them when submitting the initial message.
Sorry, disagree, I like it as is. I could see it getting spammy and giving people the ability to harass someone. I could see members sitting there for hours editing posts with removing then re-adding someone over and over just to flood their alerts. You can simply make a new post @so-and-so what do you think? just as easily.
I agree with @Amaury; the current behavior is inconsistent, and it remains one of the most frequent sources of confusion among my community members. Several people each month report their "tag notifications aren't working" when it's a case of someone having tagged them in an edit.
Of course, the person doing the tagging is not to blame - they think tagging someone will always send them an alert, yet there is nothing to indicate this will not work as expected if they add the tag via edit, making them think the person has ignored their tag. It's not a good experience for anyone, and far worse than the potential for extremely minor abuse (which can easily be confirmed by a moderator through edit history).