It’s not a job for that plugin. You need a migration script to convert the WP comments into discourse ones. I started doing this for a client once but they ended up not doing it and I can’t remember the details. I think that I had figured out (maybe there is an existing script?). Creating just the users isn’t too hard. I think I saw such a script in one of my github repos recently. (But I’m on my phone now and don’t think I can manage to look on my phone).