What is the process for lodging complaints about moderator behavior, and how is that process resolved?
The typical process is to start by flagging the post your grievance is related to with a custom moderator flag and describe what you think should be changed. You've got only 600 characters for the custom flag text, so you'll have to be brief, but there's always the option for a moderator to contact you to get more details.
Now, I know what you're thinking; "how can flagging something for moderator attention be the proper way to lodge complaints about moderator behavior?". But it is.
Let's be clear about terminology, though: "moderator", on the Stack Exchange network, typically refers to those users who are either appointed by Stack Exchange (the company) employees to serve as "pro tem" moderators on a site that is still in beta, or on graduated sites refers to those users who are elected by the community to serve as moderators. These users are recognizable by having a diamond symbol attached to their name on the site(s) that they are a moderator on, and their profile page will indicate "moderator".
Many moderation actions are taken by users who are not moderators. There are rather few things that moderators can do which ordinary community members cannot do, though moderators (those with the diamond) can normally do them unilaterally rather than having to wait for multiple users from the community to do something. This includes closing questions, deleting posts, and a number of other more or less mundane tasks needed to keep the community on track and free of irrelevant material. It's been likened elsewhere, rather aptly actually, to being elected to clean the toilets at summer camp.
If a moderator takes an action which you disagree with, then by flagging the post and describing your grievance, you bring this to the attention of the whole moderator team. And while there is nothing in the system to prevent it from happening, as a general rule, moderators are expected to not handle flags that they have a personal interest in. This can be because it's a flag on their own question or one they've answered, or a flag on an answer they've deleted, or something else. In that case, a different moderator will look at the issue, perhaps discuss it with the moderator who took the original action, and reach some kind of independent conclusion based on the facts at hand, and act on it. There are some situations where it's reasonable for a moderator to review their own actions, but it's rare. (As a corollary to this, if you flag and request a review, precisely because of this process it can take a while before the flag gets validated. Do rest assured that we check every custom flag raised, and stay on top of the others as well.)
If bringing the issue to the attention of the moderator team via a flag does not result in whatever your grievance is being resolved appropriately, then you can escalate the matter further. Typical venues in such cases is to bring it up on the site's Meta (as you have done here, but you'll normally get more positive results by sticking to the facts at hand) or contacting Stack Exchange directly (in which case you definitely want to stick to the facts) and request that they review the facts at hand. Just be aware that the people at Stack Exchange are really busy (that's one major reason why there are appointed and community-elected moderators for each site in the network) and that they might not be familiar with the culture of the particular site.
Why is there zero moderator accountability on this stack?
Well, as explained above, there is plenty of accountability if you raise an issue. Also, moderators routinely cross-check each others' actions, and will discuss among themselves if they see a moderator doing something strange. Moderator actions are also at times reviewed by Stack Exchange employees, and in cases of gross overstepping of bounds, there have actually been cases of moderators being stripped of their diamonds (and corresponding power) for violating the trust ultimately placed in them.