J. Chris Miller
From my understanding there can be only one copy of a unique in play at a time. The investigators all have the unique symbol next to their names.
However, if you want to disregard this rule, you may use the power of choice to achieve your desired result.
Not knocking this post or anything but really it's like anything else in which you can decide to do whatever you want. That said, the quoted text is correct.
I think it'd be fun to play with two of the same character to see how they fare in the game.