Regarding the specific issue
The questions and answers that were closed and deleted respectively through the community moderation threads were not about "criticising moderator actions".
The basic content of the posts were "I challenge you to prove I'm a crackpot.". However, no moderator actions were taken because he was a "crackpot", in fact he requested deletion himself, and the one single warning he got, that is now retracted, was in accordance with an old (now ammended) policy about posting off-topic comments.
To be honest, I may have called him a "crackpot" outside PhysicsOverflow, or in private discussions with other moderators, but does that really matter? I don't really remember calling him a crackpot on PhysicsOverflow in public. I apologise if I did. Whatever it is, calling someone a "crackpot" is not a moderator action as your question seems to imply.
Regarding the hiding of the meta posts
The first answer was posted on a thread entitled "Should moderators be allowed to delete posts?". There is no way that an answer saying "Prove that I'm a crackpot!" is an on-topic answer for a question about "Should moderators be allowed to delete posts?". Thus, the answer was hidden. However, the answer was reshown by you later, so since the hiding appeared controversial, and I voted to delete it instead (I had initially thought that obviously off-topic, on the verge of spam, answers can be deleted uncontroversially). The vote to delete passed with three votes for and none against, and the post was hidden.
Then (after the first deletion, but before the first undeletion), "VK" posted a question with the same content on meta. The question was off-topic for meta too, since meta is for discussion about the site, not about specific users' characters. Had the question been about a specific moderator action, it would have been fine. I voted to close it, and the vote to close went through in 23 minutes (or something like that) so the question was closed.
After this, "VK" again posted the same answer on the same thread saying "dimension10 this is on-topic so don't delete" or something to that effect. This was also before the undeletion of the first answer. I deleted it as a duplicate of a deleted answer.
Now again, before the undeletion of the first answer, the anonymous user "VK" posted a meta question with exactly the same content. I deleted it as exact vertabim duplicate of a closed question.
I don't see any violation here, as the post was clearly not about a moderator action, but the "name calling" he thinks he is a victim of.
Now replying to the question
In my opinion, yes, questions and answers should be hidden on meta if of-topic, by use of the community moderation threads. This is to ensure that meta is always for discussion about the site (including moderator actions, but not the character of specific users).
There was never any policy saying that you can post whatever you want on meta. Yes, moderators are meant to be less strict when imposing "off-topic" rules on meta, but they still do apply to meta.