I recall reading a while back that they have a procedure for this. I think they actually decide it through group consensus, so I would imagine the reasons for being fired would have to be pretty real.
Having a manager fire you gives you a lightning rod to point the feelings at, rather than an entire group of people.
There are generally 3 types of job loss:
1. People who are unethical or obviously toxic. Here, management can step in and fire the person without much blowback. If someone steals, or is a direct threat to your culture (e.g. he starts playing politics and trying to set himself up as the executive empire-builder you don't want) then it's not very controversial.
2. Good employees who run afoul of political nonsense or parochial managerial politics. This is what companies like Valve are trying to avoid, because it poisons the culture.
3. Layoffs for economic reasons.
I assume this is a case of #3. The CEO needs to explain what happened, why it happened, take responsibility for the decision, and assure people that the company will be better after the change than before.
Comment sections are essentially infinite, and if the comments are good, I don't see any reason to tell him to stop. However, if the comments are not insightful/interesting, that's another story.