Weird randart attribute

[Max Stats]

p) The Hard Leather Cap 'Feith' [2,+23] (+4)
     Found lying on the floor at 1850 feet (level 37).
     
     +4 wisdom, dexterity.
     +20% to searching.
     Cannot be harmed by acid, electricity, fire, cold.
     
     When activated, it raises your charisma at the expense of a random
     attribute.

This can't possibly be an intended attribute? It is either worthless, as in this case, or incredibly unbalancing. What if it were CON instead of CHR? Easy max HP! The idea that an activation effect can make permanent changes to character attributes just seems wrong.

[camlost]

See:

http://angband.oook.cz/forum/showthread.php?t=4097