No one gives a shit if you fired someone from your company and we really don't want to hear about your problems and issues with eachother. That sort of stuff is no one's business and we honestly don't give a shit.
The only kind of announcements I don't mind seeing is if someone is looking for a job/or a company is looking to hire someone new.
By the way, it makes your company look really iimmature and unprofessional posting absurd and/or personal beefs with ex-employees that may or may not be around to defend themselves.