Hi Alan,
The EDITABLE field isn't really intended to be toggled to change the read/readwrite state of a field; it should probably be `protected`, but is such an old part of the API that it remains available for backwards compatibility. For non-editable text, you generally want `FieldLabel`.
That said, you should be able to just use CSS to target and adjust the appearance of the element. Generally using CSS directly is the direction we're moving in in preference to the theme system.
I hope that helps, and please let me know if you have any further questions!
- Aaron