Quite often an OP has asked a question as an unregistered user, lost their cookie and come back and added an answer as an update using another un/registered account.
It would be useful to have the OP's display name (as link just like any other user) in the moderator flagging overlay as well:
It would save a lot of time (especially with questions that have more than a couple of answers) not having to scroll all the way to the top of the question to find out if the OP and answerer are one and the same.
One could just open both poster's accounts in new tabs from the flag overlay and then compare.
Merging users is probably one of the most common activities I perform as a mod and having this extra nugget of info would remove a speed bump in the process.
The same thing goes for the flag queue with the expandable in-line preview of question and answer, here's an example where the OP added an answer instead of an edit (not quite the same as described above but it's close enough to get the point across I think):