Why is the third "obviously wrong?" My dictionary (NOAD) finds no fault:
EDIT: After reading Barrie's answer, I did a little bit more research. Even though the first dictionary I checked (NOAD) had a secondary definition applied to typography, several others did not explicitly mention such a usage.
In cases where a secondary meaning is not listed, however, one might wonder if it needs to be. Some dictionaries define embolden with a definition like to help make more brave; to give courage to. With a definition like that, and no secondary meaning listed, one might certainly question the usage of this verb when applied to typeface. However, in cases where the definition is listed as, quite simply, to make bold, would a secondary definition be required?
Perhaps the most interesting example I found was this online dictionary, which defined the words as
to give courage to; cause to be bold or bolder
and when the sentence examples link is clicked, these example sentences are listed:
- Emboldened words are the sub category names for reporting the data.
- Emboldened figures are the percentages, for each house size, of the total number of households assessed.
Thus, no secondary meaning is explicitly listed, however, the usage examples imply that "to cause to be bold" could be applied either to fortitude or to text.