Whats the best way to 'splt-off' an email
<New FogBUGZ user>
From within the case, forward the email back to your FB email address with the relavant part highlighted (>>) or maybe snip the parts that don't apply. You could then resolve the original case as a dupe of the new case. You can keep resolving-dupe the case to add more case numbers...
Or just create a new case, paste in one of the items and say
Michael H. Pryor
Fog Creek Home