Simply unselect the visibility field in the field visibility scheme(s).

That's weird.  I created a visibility scheme and by default it has everything unselected.  That means, all the fields are visible to everyone.  With that understanding, I select/checkmark Visibility field and select a Global Group "Hidden" which has no member at all.

I assigned that visibility scheme to my project.  The PM logged and created an issue, the visibility field still shows up and active on his page, also the comment page.

The Developer of my project logged in, created issue, the visibility field is grayed out on his page.

The Issue Administrator of my project logged in, created issue, the visibility field shows up and active on his page, also the comment page.

The Security scheme which my project is using, it has Set Issue Visibility role assigned to no one, blank.

You need to set the visibility scheme per issue type. Edit each type and assign the visibility scheme to it.

I am not sure i know how to create field visibility scheme for each issue type? Can you please show me how? I only know how to create an field visibility scheme and assign it to a project that I want to apply to.

From what I understand, if I check mark field "visibility" in my Field Visibility Scheme (for say "No Visibility Scheme") and assign that "No Visibility Scheme" to my Project.  The turn out should be, no one (even PM and Issue Administrator) has ability to change anything in the Visibility field (the field should be grayed out or disabled).  However, what i am experiencing is different, PM and Issue Administrator still be able to select drop down menu in Visibility field when creating new issue or adding comment.

The visibility scheme that you set for a project applies only to the issues list.

You have to edit each issue type (via Administration -> Issue Type) and set the visibility schemes for create, edit and view.