Ok, there's been quite a bit of FUD in here, so I think it's time to clear things up.

You were fired for the following reasons:

1. Incompetence and not getting much work done.
2. Inappropriate or irrelevant comments/questions when interviewing candidates
3. Making incorrect comments in public about reddit's systems that you had very little knowledge of, even after having these errors pointed out by your peers and manager.
   
4. Not taking feedback from your manager or other engineers about any of these when given to you, continuing to do #2 until we removed you from interviewing, and never improving at #1.

Criticizing any decision about this program (link provided for people who aren't familiar with the program and its reasons) had nothing to do with it. Feedback and criticism, even troublemaking, are things that we actively tolerate (encourage, even) - but above all you need to get your work done, and you did not even come close to doing that.

Lastly, you seem to be under the impression that the non-disparagement we asked you to sign was some sort of "violation of free speech" attempt to muzzle you. Rather, the situation is thus:

When an employee is dismissed from employment at a company, the policy of almost every company (including reddit) is not to comment, either publicly or internally. This is because companies have no desire to ruin someone's future employment prospects by broadcasting to the world that they were fired. In return, the polite expectation is that the employee will not go shooting their mouth off about the company especially (as in your case) through irresponsibly unfounded speculation. Signing a non-disparagement indicates that you have no intention to do this, so the company can then say "Ok, if anyone comes asking for a reference on this guy, we needn't say he was fired, just give a mildly positive reference." Even if you don't sign the non-disparagement, the company will give you the benefit of the doubt and not disparage you or make any negative statements first. Unfortunately, you have just forfeited this arrangement.