Quote Originally Posted by ObliviMancer View Post
Not sure if it has been done, but the Weapon Proficiency feats does nothing. The "Benefit" does not grant "proficiency", it simply states that you make attack rolls normally. It then tells you that normally you take a -4 penalty.
Lol. Good one.

The PHB however clears up that this is not what the normal section tells us:
Quote Originally Posted by PHB p. 89
Normal: What a character who does not have this feat is limited to or restricted from doing. If not having the feat causes no
particular drawback, this entry is absent.
"Normally" in the description can only mean without penalty for non proficiency.

There is a quirk though. Since the feat does not make the character proficient but only removes the penalty, the character would not qualify for any other feats or classes that require proficiency