See this answer. But with a serious caveat.
This is another one of those instances where a reasoned design stance has turned into some sort of dogma. An occupational hazard of having a guru at the helm. People like clear answers and the courage it takes to give them. But clear answers have a way of becoming dogmatic and unreasoned over time. We don't maintain that our way is exactly the right way (anymore). It still comes back to design trade-offs, and you find yourself on the wrong side of one. You're not alone.
In the debate about required fields, we have made a trade-off that favors flexibility and openness over control. People who want required fields (or Bugzilla-style blocking) find themselves on the wrong side of our trade-offs, and have to figure out for themselves whether the advantages of FogBugz are worth giving up required fields, or if this is a true dealbreaker.
What I've come to call Notify functionality, though, occupies a different space. Let's call it possible-and-necessary-but-hard-to-do-well. It's the same space Case Event Editing used to occupy before one of our guys fixed it for 7.3. And the same space that true historical reporting used to occupy before FogBugz 8, now in limited beta. Seeing a pattern here?
The lack of Notify functionality has come to be a liability. The design trade-off we made--to err on the side of fewer emails--is limiting us more and more as the months slip by. Someone will take up this challenge. It's just a matter of when.
Update: The Notify feature has been implemented as a plugin to be released in an upcoming version of FogBugz.