To protect your Blog from automated spambots, this plugin adds invisible formfields to your comment form.
The best way to deal with this Problem, is to uninstall the Plugin via the WordPress Backend and re-install the Plugin.
Update to at least Version 3.14. Since this Version the Options are not rested when the plugin is updated.
NoSpamNX does not work with OpenID.
NoSpamNX does not work with BuddyPress.
Yes, but you have to activate the plugin for each site individually.
Yes, just add an IP-Address (e.g. 10.23.23.4) in the Blacklist or use CIDR-Notation (e.g. 10.43.8.67/28) to block IP-Ranges.
No, the plugin focus on automated Spambots only and I have no plans of changing that. There are some really good Plugins in the WordPress Plugin Repository which can do that for you.
Due to the functionality of NoSpamNX false-positives are nearly impossible. There 'might' be problems when using WordPress Cache-Plugins, but none have ever been reported. If you are uncertain, mark Spambots as Spam instead of blocking them.