Is this possible to display a different name on the main site and on a subsite?

Hi,

My question is about a multisite network using Pro Sites, New Blog Templates, etc.

If a user creates a site within the network, he can choose if he wants to use his name or a nickname to publish content on his blog.

What if he wants to use something different on the main site?

On the main site there's a forum and one user wants to use:
- his real name on his site,
- a nickname on the forum (on the main site)

Is this possible?

Best Regards