If you read the DEV tracker and what Feather has said about it you will find that, indeed, Festival Glaciation was nerfed hard by the incorporation of ML increases. Before U16, old Glaciation effects translated into spellpower with U14 with no ML increase. Then the items had the glaciation festival effects wiped from them by a bug (a rather big coincidence considering the nerf that followed) and the motes/recipes refunded.
So, Glaciation will increase the ML of random gen weapons when you apply one that would exceed the current ML of the weapon if it appeared on a lootgen weapon by itself, without a suffix. Also, you can no longer place Risia glaciation effects on the Eternal Wand of Frost.
EDIT:
While I could indeed apply the original Risia Glaciation upgrade to a random gen weapon, it didn't allow the Midwinter Festival Glaciation to be placed on it.