Question about Steam (valve)

If anyone with a steam account can answer this question, I'd appreciate it.

I know that you create a permanent account name, and I know that you then create a nickname, for playing online, which you can change at any time, but which name is used when you post on the steam forums, your account name or your nickname?

Thanks

 

You use your account name when posting in the Steam forums?

Wouldn't that be a security risk?

 

Ha

1. account name
2. nick name for multi player
3. screen name for the forums

OK, thanks