It's true that if you delete the attribute from the form and then add it back, it will revert to the attribute-level presentation options.
However, if you then edit the attribute-level presentation options, the changes will not be reflected at the form level, unless you actually save the form after deleting the attribute from the form. In other words, it's not enough to simply click on OK and then add the attribute back. You have to delete the attribute, then save the form and then add the attribute back. Otherwise, it will still be considered to have a custom presentation.
I wouldn't mind this so much if AwareIM gave a clear indication (or ANY indication for that matter!) of whether or not you're using a custom presentation for a given attribute on a form. Presently, there is no way to tell whether or not an attribute has a custom presentation.
I would suggest that if an attribute has a custom (form-level) presentation, that the attribute name appear in a different color in the Form Layout Editor. Also, in the screen where you define the presentation options, there should be a "Revert" button that would revert the presentation to the global settings. That button should only be enabled if in fact the attribute is using a custom presentation.