The Scycthe of the White-Eyed Omygodthisnameisfartoolong does not seem to respond to Sharpness enchantment, nor to the Wrath (forbidden magic) enchantment.

A Sharpness 5, Wrath 5 Scythe still deals +14.5 damage.

Enchantments work fine, I tested em on a bunch of other modded weapons. Only the scythe does this.

Is the scythe actually dealing that additional damage it is supposed to deal with the corresponding enchantment, or is the damage just fixed to 14,5?

The damage is fixed, it doesn't one shot endermen with full enchantment.

Fixed for the 1.8.9 version