Almost every software company I've ever worked with had this insidious "priority inflation" that couldn't be stopped. It works like this:
We start out with some sensible definition of priority for bugs: P3 = nice-to-have, P2 = low-priority-but-ship-blocking, P1 = emergency-fix-this-now. Bug intake goes on for a while under this system. Some bug filers don't feel their P3 or P2 bugs are getting worked on, so they "promote" those bugs to P2 and P1. That'll show those engineers my bug is important! Now we seem to have more and more P1 emergencies going on, and the team is struggling to just get through those. Nobody knows which ones are actual emergencies, and which ones are just "somebody being passionate about a bug".
Soon, we get an actual pants-on-fire production emergency. This emergency is more urgent than any P1, so we call it P0! Now we finally have a way to mark real emergencies, because the bug database is now overflowing with P1s. Soon people realize they can deem their favorite bugs as really-really-important, so they promote them to P0. Eventually, the database is now overflowing with P0s, and nobody knows what's really urgent. Then another real pants-on-fire production emergency happens...
I worked at a shop with P0, and then there were too many P0 tickets, and then you just worked on whatever the CTO told you was the _actual_ highest priority ticket when he stopped by your cubicle for a chat.
1) Allow developers to change the priority, i.e. downgrade P0 to P1 or P2, with all subscribers notified. Optionally, always downgrade to the lowest possible priority.
2) Shame people for inappropriately using P0. After a few strikes, remove their ability to do so.
We start out with some sensible definition of priority for bugs: P3 = nice-to-have, P2 = low-priority-but-ship-blocking, P1 = emergency-fix-this-now. Bug intake goes on for a while under this system. Some bug filers don't feel their P3 or P2 bugs are getting worked on, so they "promote" those bugs to P2 and P1. That'll show those engineers my bug is important! Now we seem to have more and more P1 emergencies going on, and the team is struggling to just get through those. Nobody knows which ones are actual emergencies, and which ones are just "somebody being passionate about a bug".
Soon, we get an actual pants-on-fire production emergency. This emergency is more urgent than any P1, so we call it P0! Now we finally have a way to mark real emergencies, because the bug database is now overflowing with P1s. Soon people realize they can deem their favorite bugs as really-really-important, so they promote them to P0. Eventually, the database is now overflowing with P0s, and nobody knows what's really urgent. Then another real pants-on-fire production emergency happens...