The ban algorithm is automatic by the StopForumSpam filter --
I've never had to manually ban an IP address, so you can bet I never had involvement
Often, a shared IP address might have been abused by a different user on the same ISP, or some other metrics (e.g. multiple abuses coming from multiple IPs on the same subnet), or other heuristics. You might have been hit by this, or this may be a false positive of some kind --
A few years ago, we were hit by spammers posting hundreds of messages (in Chinese) in the period of an hour, so we had to find a solution to automatically blocking such spammers. We cannot go without an antispam plugin, but we may be able to switch to a different antispam plug-in that is less likely to "throw the baby and bathwater together" by accident.
What's the usernames of the banned accounts?
You can also send me a PM or contact squad[at]blurbusters.com for further troubleshooting too.
[if the emails can make it through...but try a PM]