Is "Search Multiple Content Types" broken for anyone else?
I'm assuming that it is broken, but it may just be missing a feature.
Anyway, the "Search Single Content Type" has an option to "Find Posts by User" and "Find Posts Started by User" and defaults to the former. The "Search Multiple Content Types" seemingly doesn't have these options and defaults to "Find Posts Started by User".
That kind of makes it useless to my mind.