I add a contact by adding in a Yahoo ID, and the screen name turns out different

Hello, just registered to BBB because of a nagging question that I have.. I apologize if this has been addressed earlier, Im new to Yahoo! Mesenger.

I added someone into my Yahoo! messenger using a Yahoo ID. Example “johndoe123”.

Well, when I did the screen name that appears on my Yahoo Messenegr winds up being something like a full name for example like “michael barton”

But the thing is, Ive talked to this person before, and he/she says that her real name is “john”, and that everyone that has added him/her into Yahoo shows up the same “michael barton” as a screen name on their Yahoo Messenger.

1) Should I be worried about this? Does Yahoo do this all the time?
2) Any reason why Yahoo does this if it does occur commonly?
3) If this is not a common occurance, then should I be worried that “John” is some stalker or psycho?
4) Is there any way to verify “john”‘s identidy over something like this?

Any feedback is greatly appreciated.

Thanks!

stonesnbones