[WhaLberg]

For default vBulletin, there is no option for users to decide displaying or not the extra profile fields. First of all, to make a field private or public, there has to be a column in the profile field table. Second of all, if the user sets the fields private or public while registering or editing the profile, there must be an update for the field. Third of all, while viewing a member's profile, it has to check if the fields are public or private to return true or false. Then in the template, you should set your template condition like <if condition="fieldispublic">show the fields</if>.

So, what do you think now? Is it just a condition based on the field private/public option? At the end, yes.

But, you can also make the profile field private and set "Can View Private Custom Fields" to No for some usergroups.