Since Luna's Lunar Blessing improves base armor by a percentage and adds it to Luna's and affected allies' base armor instead of it being bonus armor, I (and apparently some other players) have found out that any armor reductions that Luna (or her allies) gets are also increased, based on the level of Lunar Blessing. Here are some examples (please excuse the images being excessively big):

You'll notice that Luna is losing 10 armor from an activated Mask of Madness, but it's supposed to reduce your armor by 8. Lunar Blessing adds 25% extra armor, so here it also amplifies the armor reduction of Mask of Madness (25% of 8 is 2, so 8 + 2 = 10)

In this case, Shadow Fiend is supposed to be reducing Luna's armor by 12 (level 30 Shadow Fiend has the +5 Presence aura armor reduction talent as well), but instead, she loses 15 armor.

And obviously, this effect just keeps stacking with more and more armor loss (and it'll also happen with other things like Assault Cuirass, Bristleback's Nasal Goo, etc.)

And anybody who's affected by the aura will also be subject to this. In the previous image, Luna is losing a total of 31 armor, instead of 25 armor, and here, Mirana is losing that same amount of armor as well.