Custom fields still searchable even if hidden in field configuration

Custom fields are still searchable even if they are hidden in field configuration. It sill display if the field is in context. This should work similarly to other systems fields where it's not shown if it's hidden in all currently relevent Field Configurations.

This can lead to the mis-conception that hidden fields can be a useful way to have read only custom fields (see JRA-8344). You should use screens to achieve the same effects instead.