Username recovery for identity.kde.org

[Alessandro Polverini]

Hello,
I'm sorry to write you but I'm stuck, unable to login to 
identity.kde.org anymore because I've lost my username, how can I 
recover it?

I've tried every way but it seems there is no way to recover it.

The only recovery option available is for the password and it asks me 
both the username and the email address.
I know the password, but I don't know the username!

I tried to register a new user but the system won't let me do it because 
it says that the email is already taken.

This means the email address is (unique) key in the database, so why 
can't I use it to login instead of using a username?

Can you please help me getting out of this situation?

Thanks :-)
Alex