Who knows. There are so many algorithms and people at play in the decisions to ban things on large platforms that most people that work at the organization itself won't even be able to tell you who or what, specifically, was responsible.
That's why this gets posted to HN with hope that enough relevant people will notice such that remediation has a real chance of occurring, because with a normal 'appeal' your chances are basically nil regardless of how incorrect the ban was.
If I had to guess at a moment's notice, I'd say some kind of spam/malicious content tripped some kind of automated trigger. Hopefully it can be fixed soon. Usenet unfortunately harkens back to the era before there were bad actors at all and thus has the same vulnerability to spam and other issues as email does. I bet it's something along those lines.
