Translation:Το πρόσωπο του είναι όμορφο.
«πρόσωπό του» double accent because of «του» or the rule is changed?
The rule applies, it's a small mistake in the sentence.
The second accent on πρόσωπό shoud definitly be added, I think.
The original sentence can't be changed now, unfortunately, but the alternative with the second accent is also accepted. ^.^