I'm not sure how, but it seems enchanted books and enchanted items have descriptions when this mod is installed.
I already have a mod that handles this in my pack so I would like some way to remove it.

It seems to be from the l2core jar-in-jar. Perhaps this side effect of installing the mod could be put on its mod pages?

You can disable this in l2core config (in l2configs folder)

Which mod are you using for enchantment display? Is it causing double enchantment tooltip? If so, please inform me and I will try to fix it. Some of my enchantments have custom tooltips that read numbers from config, and to make it work I have to have a builtin enchantment description feature and it should override (instead of append to) other mods' enchantment descriptions.

Yeah, I disabled it. I was using https://www.curseforge.com/minecraft/mc-mods/enchantment-descriptions at first, but decided against having it on tooltips altogether, and instead using EMI Enchanting for that purpose