Changing your Nickname

[Jackson Cage]

I swore I saw an option for this but I can't find it anywhere.

I want to create a board where the members can have some. Post messages and change their Nickname so no one knows who they are, is there an option that allows them to do this ?

[Amacythe]

No, this isn't an option.  When you change your name it changes for ALL posts, and when you change it back, it again changes for all posts. 

Have you considered allowing guests to post to an anonymous board?  That is about the only way they can do it and even so, the Admins would be able to see who they are by checking the IP address associated with that post.