The name you use is independant of your login. The reason for this is that you can have multiple names registered, clan tags, etc.
So if you had name1 - name3 registered and a clan with the tag [tag], you could log in under "name1", but play as any of the following:
name1
name2
name3
[tag]name1
[tag]name2
[tag]name3
Plus you can add non-alphas and such to your name as well, like:
-*[name1]*-
or whatever else you want to throw in there. Almost an infinite number of possibilities.