Differences between keen edge spell and keen weapon property

[Strife2002]

Was the keen edge spell not meant to function identically to the keen weapon property? The spell allows projectiles to be affected by it and, technically, ranged weapons since it leaves out the word "melee" in its description of weapons that can be affected. The weapon property, on the other hand, specifically says melee only.

Also on a related note, would a dagger with the keen weapon property that is thrown still use its improved crit range, since it's technically being used as a ranged weapon?

[Drejk]

The spell is more versatile than the keen property. It happens - e.g. haste spell grants more than speed weapon quality.
Thrown weapons use the same damage and criticals as in melee so keep weapon still applies - it does not magical vanish from the light melee weapon part of the weapon table.

[Charender]

Also, keen does not count as a +1 enhancement, and thus does not count against the +10 total enhancement limit on weapons.

[Grick]

Charender wrote:

Also, keen does not count as a +1 enhancement, and thus does not count against the +10 total enhancement limit on weapons.

Keen Edge spell, correct, Keen weapon property, no.

+5 Vorpal with Keen Edge spell = ok
+5 Keen Vorpal = not ok

[Thorin_Ironwolf]

I am miffed by the spell Keen edge V.s. the ability Keen for projectile ammo. Why can we not make arrows keen aside from the fact that the keen ability says Melee weapons? I can use an arrow as a melee weapon can't I?
I don't understand why this restriction exist.