There are plenty of tickets regarding the hidden field usage in the Customer Portal and it is being addressed.

Adding onto that, it would be nice to have an indicator on Custom Fields that show (at a glance) which fields are hidden or editable in the admin menu. Otherwise, to know which are which you need to go through the fields individually and/or on the portal itself. The fields already have an indicator for what format they're in (text, date, number, etc) so another indicator for hidden/editable would be greatly appreciated as it would save a bit of time when these fields need edited.