Sorry for the late reply to this. The category that RSS feed items get posted to is based off the domain that is used in the feed item’s link attribute. It is not based off the domain of the RSS feed. For example, if your RSS feed is at www.example.com, but the link attribute in your RSS feed is pointing to blog.example.com, you would set the category for the feed by adding a host entry for blog.example.com.
If people are running into issues with RSS categories that can’t be solved with the above approach, let us know and we’ll look into what is going on.
I will update the copy that is used by the plugin to make it clear how to set categories for the feed’s posts.
This needs to be fixed. The plugin should not continue to create topics from the RSS feed when it is disabled. For now, you should be able to stop topics from being created by deleting the host entry that you have set for the plugin’s domain.