Regarding the impersonation, it was me being cautious, I didn't do any consultation or something like that.
My take is that the consequences of X threshold of people complaining about that would be a major issue, including possible requests for deleting all the issues migrated that contain the impersonation, and I don't want to find myself in that situation. If that surprises you, I suggest to take a moment and think again about how many different people our community have :). On the other hand, less legible text of migrated issues doesn't strike me as a major problem.
For practical reason I personally prefer the result of the migration with impersonation too.
Anyway, Philip let's go with impersonation, would you be able to take care of that?