Does it contain any days/duration on your ban? If so, then it's probably due to low-quality posts/spamming even though it's on your local board. There are still certain rules on local boards even though it doesn't affect the main board, and it might be that your moderator/other members on your board reported your posts.
Probably so. I took a look on your posts and I didn't understood it simply, all of them in the local board, but some of them are really short, which is actually normal for local boards. So I am agree with this opinion that someone reported to a forum moderator.
Hope that you know that there is no chance to come back your account. I have met only one guy who really could to manage it on the forum but it took over than half of the year of appellations and proves.