I just noticed that if there are messages containing æøå (probably other non-ascii characters as well, but these are what I have observed), and they are signed with a key that I have not imported, then those characters are simply omitted.
So for example the string: 'på tørn ære' will be shown as 'p trn re'
However - once the corresponding key is imported, it shows correctly. Which is rather surprising, but leads me to believe that the fix is likely fairly easy.