Thanks a lot for you work. This plugin is very helpful. But it can confirm the bug report of Dani, the "Digitally sign messages (by default)" setting doesn't work. I'm using v.0.3.0, but not the "Virtual identities" add-on.
This plugin does only change the configuration-dialog, nothing else. Thus the reason for "Digitally sign messages (by default)" not working has to be somewhere else. (For me it's working like a charme.)