more than one person w/ same user name?

There are plenty of Y!A posters who have the same name. You don't need to choose a unique name when creating your account. There can be 20 people named "Mike D" or "Yahoo User" or anything else

As others have stated, any username is available for use, even if it's already being used by someone else. What if two people had the same name? It wouldn't be fair to say that one of those users was unable to use their own name.

If this other guy is answering questions that you answer, or answering loads of questions in the same categories you frequent, and is *pretending* to be you (by using the same writing style, etc) then that is considered impersonation. That should be reported on his Pulse page. However, if he's just doing his own thing and not hurting you, then you shouldn't be worried.

If he does cross over to the "dark side," you can always change your profile picture and/or use a different username, to avoid confusion.

Anyone can have any name they want; however, if said user is pretending to BE you that is impersonation. Your username is something I could imagine being picked twice out of all the millions here.

Only specific posts can be reported, not blanket users. Don't worry about it too much.

You can use any nickname you want, even if someone else is using it. Yahoo will sort it out using IP addresses.

Just look back to the "Edna" debacle here on Y!A. There were literally hundreds of trolls using the name "Edna".