my cited violations were very shaky and reasonably characterized as an overreach of administrative regulatory authority.

You say this like Reddit has a system of laws protecting your rights.

I'm not taking a side on your shadowban nor whether this is appropriate or not (re-read that: there is no opinion here, just pointing out reality). That said, this is a site operated by a group of people, the admins, who unilaterally decide what is or what is not what they want on the site. That's just the way it works. Everything from the comment section of Breitbart to 4chan are the same way. If the admins woke up tomorrow and decided to rebrand Reddit as a site where only discussion of dickbutt is permitted and anything else is banned, they can do that. This is very much not your playground. It's (mostly) their code, their servers, their network infrastructure, their bandwidth, and their money.

Because of that, you cannot call something an "overreach," because there is no limit on their power. They self-impose limits in the guidelines of Reddiquette and actual site rules and unspoken wishes (because they want to keep an audience, as it is in their interest). People talk about free speech vis-à-vis the First Amendment to the United States Constitution a lot and get this wrong, too.

My point is merely to be careful about approaching something like your shadowban as if your rights were violated via an "overreach," or otherwise assuming entitlements that make sense to you under your system of government such as free speech, in an environment where you have absolutely no entitlements. If Reddit had a contract with you saying they would only ban you because of (X), (Y), and (Z), that's one thing, but they do not. They could ban me for this comment if they wanted, and I could appeal and fight it, but in the end it is their decision on their sandbox.