From the looks of it, trust seems to be the main issue; not just trust with the moderators, but trust with your fellow poster not to try to twist things against you.
How do you fix an issue of trust?
Say you have a post deleted, and you e-mail Paizo asking why. If you are told
"We are sorry, to protect your confidentiality, we cannot tell you any details as to why your post may or may not have been deleted, nor can we even confirm or deny that we did delete one of your posts,"
a)Whoever wrote that e-mail (and possibly whoever wrote Paizo's moderation policies) is ignorant of what confidentiality actually is, or
b)Whoever wrote that e-mail is lying.
If no one at Paizo honestly knows what confidentiality is...there are a lot of ways they could find out. I don't really think we need to delve into this possibility. It certainly won't instill much trust of the mods in users.
If you find out that Paizo has sent the same nonsensical response to many users over a long period of time, it sends the impression that Paizo has a policy of lying in responses when asked about moderation decisions. And that, too, is not a good way for Paizo to build a reputation of trustworthiness.
If, on top of all that, e-mailed responses you get from Paizo are laced with personal insults, it becomes really hard to believe that whichever moderator is e-mailing you can enforce the Community Guidelines.
Everything I just said only applies to trust in moderators. As you pointed out, trust in other users is an issue as well, but it's an issue I have absolutely no idea how to address.
Or it could be (c) they intended to say they were protecting the other poster's confidentiality and simply misspoke/mistyped.
I cannot speak for the moderators here, but when I administrated several games and had to discipline someone, for whatever reason, we customarily didn't disclose what had happened to other people that we had to talk to, in order to cut down on the "why did X get that punishment and Y didn't?"
It's hard to consistently do a job like that and not have a level of distrust from users who are upset that their friend got punished or that the response they got wasn't as clear as they'd like. But it breeds what we're seeing here, with calls of lying, of favoritism, of corruption. None of those things are easy to disprove once the rumor mill starts up.
Regardless of how you feel about the mods or other posters, if your post(s) get deleted, it isn't the end of the world, or even that bad of a thing. You shrug and go back to that conversation or another and try not stray towards whatever got the thread removed, the posts taken down, and so on. We have to negotiate the same mine field in real life with other people. I'm not sure why it has to be so hard here.