I've searched online quite extensively, and it does not appear to be possible. I figured I'll ask the experts before I give up.
In a browser form, is there any way to allow the users to format non-rich text fields themselves? For instance, our HR person would like the ability to highlight a field if it matches a certain criteria (that does not really fall into the realm of using rules to do it automatically). It's more of a subjective decision on her part.