How do users escalate concerns about an abusive employee?

In theory a MSE mod ought to be able to. In the post announcing the appointment of the moderation team

Our appointed moderators will have full agency to correct any chain of correspondence that appears to be going off the rails, no matter who was originally driving the train. Sometimes it's better to let an objective party step in and handle things, we'll just leave it at that.

However with recent events, I'm unsure how it would work. Its probably a conversation we need to have in the near future. I never bothered to ask cause I figured it would never really be needed.

If there is such a path - there's a few other (minor) issues to sort out, like how you would contact a MSE mod discreetly.

In theory I could email folks in the CM team (or to community - but I don't think the usual fire and forget approach to that account works here. In these situations a reply is essential and its not guaranteed in any way), but I'm not sure if its the right thing, and how it would work with higher level folks involved.

There have been a few proposals to have a paid(?), neutral ombudsman role, or a speaker for the moderator community that might have promise too.

While I've traditionally been opposed to the former - assuming the ombudsman was in a position of trust and independence, at this point that seems a reasonable way to do it.

To borrow another part of that post

In a dynamic where we essentially hold all of the cards and power, we need to give folks as much latitude as possible in order to create a field that's as level as possible. That means, we've gotta let the truth hurt, essentially, even when it's incredibly inconvenient. HOWEVER, if we can't find a trace of good faith in correspondence or it has become personal, it needs to be removed to keep the bar to entry in line with what we can take.

Having such a mechanism would probably be desirable - if nothing else, as a way to get feedback before things go monumentally wrong.

There is no formal way for users to complain about employees. If there were, it would be in the help center. This lack is by intention.

While these sites are built to appear to be a community that is democratically created, shaped, and governed by its members (or "users"), and the company is designed to appear as the natural extension of this self-governance and to seamlessly integrate users via moderators with the Stack Exchange employee team, there is a blood-brain barrier between users and the company that users cannot overcome.

Stack Overflow and Stack Exchange are a business, and its users are customers. In the same way that Amazon or Facebook do not disclose who works there, what they do, and how you might talk to them, SO/SE keep their internal structure and inner workings hidden on purpose, because that keeps customers slipping off the smooth surface of the help center and contact page.

If you believe that one employee is misbehaving and keeping any complaints to reach that employee's superiors, you could email one or several of the higher-ups whose email addresses are published in their SO profiles. If they care they will intervene.

But given how SO/SE handle the recent events, it is much more likely that anyone who might be responsible for your matter is already aware of it and that you aren't dealing with a single person being obnoxious but with official company policy. In that case you could involve a lawyer and/or (threaten that you will) go public. Nothing less will get you a reaction from an internet business like SO/SE, Facebook, or Amazon.

tl;dr

As a customer, you are not part of the company structure and its channels of internal communication aren't open to you.

Given that StackExchange seems to care more about what people with many followers on twitter say than what is said on meta by the likes of me, it seems clear what is likely to work. Most of us don't have enough followers on twitter to make it worthwhile trying.

Recently it has become clear that StackExchange has an issue with "group think" that matches the views of the member of staff that I think the question is asking about. Their actions have already been communicated well to management, hence I don't believe additional "nice" communication will result in a change of how the given member of staff is managed.

Note I am not saying it will be of benefit to use twitter, or worth the effort, yet alone risk damage to a site you care about. I expect the "war" will not be won/lost on StackExchange and putting StackOverflow in the public firing lines will not change the outcome.

First of all, there is no way, obviously. I've asked about this from the moderator perspective in Feedback post: Moderator review and reinstatement processes.

CMs and other employees are above us. It's a company, and in team eyes an employee is always in better standing than regular members.

Of course, you can report violations via Contact form. But you will get only a formal reply or will be ignored. This is not my guess, I had this bad experience myself. The contact form doesn't work. One thing to mention here, if you have problem with a CM and send a message via this form, he/she will be able to read this message.

Also, you can try to send an email directly, for example, to Jon Ericson or Tim Post. I have not communicated with Jon, so I can't tell anything about him, but, in my experience, Tim, at least, will try to listen you.

The process is that you post publically: Is there a way to appeal decisions made by the Stack Overflow Support Team team members?

As an example, there was a user's (initials RC) complaint that 'in chat he flagged an all caps message and was suspended'. We have been asked not to link to that Q&A, it's resolved, water under the bridge. The accepted answer has 25+/1- votes, and contains the words "has apologised".

It is possible to complain publically (and politely) about a high reputation Community Manager and receive a satisfactory outcome.

... how can I protect myself from also being targeted as a whistle blower?

Theoretically people are professionals and barring the occasional mistake or off day you are expected to trust that a rational conversation will lead to a rational outcome.

That may not be the answer that you wanted, in which case you are free to write your own answer and accept it, but that is the answer that Stack Exchange has provided in the past and there are examples of that working with CMs (and on the various child metas with moderators).

The other possibility is an anonymous email. You probably knew that already.

I don't think us users can do much, we've made the site and now SE no longer needs us, random users from the web arrive, read questions etc and the old users who built the body of knowledge... well, thanks for all the fish.

The main thing we can do, as users, is affect the SE brand. Bad publicity might be good too, but these days companies care a lot about how they are perceived; that's why you have so many adverts designed to tell potential customers that the company shares their currently-fashionable values on climate change or gender or whatnot. If SE starts to be perceived as arbitrary and unjust, they'll wake up and do something to repair that damage.

The other thing a particular user could do is contact an attorney for what many have decided is outright defamation. A legal case would have to keep everything here quiet for a lot longer, but we'll find out what happened when its over. It would also force SE's hand to resolve this one way or the other.

There is a formal arbitration option, open to any SE user who feels they are in conflict with Stack Exchange. There is a checkbox on the form that one can use to indicate a request for mediation.

Please see my post describing the process, cost, etc.: https://meta.stackexchange.com/a/334482/287826