That plugin won a prize in 2008, but google reports known security vunerabilities.
Had a look to it's code to see how the author managed to add a tag taxonomy to standard WP comments and mostly seems an hack, no idea if that part would work on the current architecture.
The plugin is declared to be working with WP 2.5.1 (!) and I'm not sure about how WP comments internals changed up to 3.5.
I'm exploring this part and at first tought that comments could be just a custom post type and extensible as such, but a first look at WP core gave me the idea that it isn't like that.
If I'm not wrong we can easily add custom fields to built-in WP comments but using a native tag taxonomy is not supported.
How would you implement that otherwise?