I've gained two of the same ones since my last post, bringing the total up to five in a row. I also have twelve Moderate Inner Light enchants from stash room pickups. This leaves two possibilities I can think of.
-Truly bizarre luck
-A problem in the enchant seeding, maybe due to being a pre-572 world or something else entirely
I DO have one dissimilar enchant (same base enchant + Emits Light, which is equipped) which I gained from the enchant containers picked up before upgrading to 572. I forget whether I got it retroactively or upon grabbing the first container in the new version. At least I know it's not a completely consistent problem.
I like the idea of forcing enchants to differ, even just a little. But it may just be me