What's your definition of legal action? I generally understand it to mean a filing, legal proceeeding, etc.
A simple letter does not, in my mind, constitute legal action.
A letter could threaten legal action, but that's explicitly not what I'm suggesting should be done here -- you don't want to attack FB lawyers, you just want a side-channel to a reasonable set of people who are interested in avoiding litigation/bad press, and powerful enough to do something about your problem.
[EDIT] - responding to your edit.
> Meta has a large legal department full of lawyers who are paid a lot more than whoever you can afford. They are used to dealing with threats and actual lawsuits every day from people, companies and governments all over the world. Your random letter isn't going to scare them into submission. You will simply get back a templatized response along the likes of "We reserve the right to ban anyone from our services. Here is a link to our ToS."
They're already getting nowhere with dealing with the current level of automated response/remediation. I have explicitly noted that the point is not to scare the lawyers (everyone seems to be projecting this into my suggestion), but to possibly get the ear of reasonable people with power.
Regardless of what you think will happen, it is an avenue to try, that evidently the OP didn't think of yet.
[EDIT2] - I see now that I wrote "legal action" and it's been interpreted as such. What I meant was to "send a letter" that may be received by someone reasonable with power to fix what is likely a simple moderation mistake. I am not advocating trying to take Meta to court.
