Ah, pure insanity, the kind of boundary pushing I like to see in my shounen.
I really liked the conflict presented with Link, a great depiction of another Gray-man.
So, I think my fears from the last chapter were fortunately squashed with the whole mirror scene, with a bit that I'd kinda expected and a good bit I didn't.
Mana devouring Nea was a nice surprise, and the perfect explanation for Mana returning to the 'default' Millennium Earl. Gets rid of the 'replicated Earl' theory that felt shaky(still doesn't explain the panel with Mana holding Nea as the Earl attacks him..just symbolism?) And what I really liked was that it took the route I was hoping for, Mana being swallowed by his Noah memories(after devouring Nea), and losing himself to his guilt to the point he subconsciously renounced his name within "The Earl". That guilt allowed what I'm assuming to be the consciousness of Adam within(aware of both Mana/Nea, and every other normal Earl) to take control, reverting "The Earl" to a default,(hinted at last chapter by Wisely) swallowed by Noah memories and blind, insane desire to destroy the Heart and invoke the "Three Days of Darkness". So Adam throws both "Mana" and "Nea" away from "The Earl", which brings us to Allen and the Mana that raised him, a hollow, grief-crippled and confused shell(Which means the Akuma-Mana plothole is filled already, sasuga Hoshino-sensei!)
And even more verification on why The Millennium Earl began to feel strange upon meeting Allen. Not because of Allen/Nea at all(well obviously eventually this is the case) but because "Mana" must have returned to "The Earl" after being resurrected and destroyed by Allen. A perfect silver lining for Allen's character, as well as a nice coincidental slap in the face to Adam and his default Earl.
The shitty side of all this is that it all still points to a bad end for Allen. Unless, somehow when "Mana" becomes fully assimilated with The Earl(whatever that will look like), Allen is able to reach him as his Mana, trumping Nea and Mana's connection. Seems a bit too shounen though.
I could see the remainder of DGM chapters spent simply explaining how all this works...