This are a custom area inside the XSL files that are user-editable via the designer, but not to the level you are talking about.
The first suggestion would be to shorten the hint text so that it doesn't need to wrap.
Outside that, if you want to modify these, you will need to go into the XSL files, locate them, and make your modifications there. Search for the text "optionalPlaceholder" and to the style attribute as necessary. Custom changes to the style attribute should survive a round-trip in the designer.