I remembered something that always bugged me: there are identical spells with the same name. Greater Feather and Ulms's Juicedaw Feather, for instance. They both have a Feather spell, both with identical magicka cost, magnitude and duration, and which are both sold by Ranis Athrys.

Does anyone else find that really strange?

*nods in agreement* A number of spells are identical if you look in the CS. I just try to pretend the spells come from different 'magic traditions' and just happen to do the same thing. *shrugs*