- Angst Aversion: Some feel the Bittersweet Ending was too cruel/dark, and that Celestia and Mirror Sombra should've at least gotten to say goodbye on more-closure-y terms.
- Base-Breaking Character: Princess Celestia. For some, her selfish and short-sighted actions in her younger years have driven away any amount of sympathy; for others, her deep regret over it and portrayal as The Woman Wearing the Queenly Mask make her a far more interesting character.
- Broken Base: Ho boy, the issue broke the fanbase into as many pieces as there were left of the mirror. To recap some of the issues discussed:
- Was Celestia and Sombra's romance a tragic case of Star-Crossed Lovers, or a blight on the plot?
- Was Sombra's Heroic Sacrifice a Bittersweet Ending, or a Deus ex Machina Anti-Climax and an inter-dimensional invoking of Status Quo Is God?
- Does Star Swirl's friendship with Celestia invalidate the other information revealed about him, or just add depth?
- Most wanted a story that focused on the Prime Mane 6 fighting their alternates and were disappointed when the story didn't deliver. Others actually didn't mind this since they though the focus on an alternate Celestia made for a more interesting threat since they pretty much fighting a "goddess" and that it was a good parallel to the start of the series where they fought Luna.
- Dork Age: Disappointment over this arc signaled the start of one for the main series: most issues after this have had mixed to bad reception, with the better ones viewed as So OK, It's Average by fans left jaded.
- Ensemble Dark Horse:
- Epileptic Trees: Some fans have taken it upon themselves to expand the mirror universe, mainly by fleshing out the characters that only had brief cameos.
- Harsher in Hindsight: The Reality Bleed between the two universes. Come My Little Pony: Equestria Girls Friendship Games, and a certain One-Winged Angel threatens to do the exact same.
- Hilarious in Hindsight: Several comparisons can be made between this storyline and Inner Glory. (Evil/opposite Twins of the Mane Six, a Magic Mirror leads to an alternate universe, ect.
- Romantic Plot Tumor: The actual conflict between the two worlds takes a back seat to exploring Celestia's relationship with the mirror world Sombra.
- They Wasted a Perfectly Good Character: See all those Mirror Universe counterparts on the page image? Yeah, you're not gonna see any of them actually take part in the story: Chrysalis and Derpy only appear via depictions of them in stained glass windows, the alternate versions of the Mane Six and Cadance and Shining Armor only make a cameo on a splash page in the last issue, and that same splash page is the only time the Doctor Hooves of either universe is seen.
- They Wasted a Perfectly Good Plot: The limitless potential offered by a Mirror Universe plot was squandered by focusing on a romance between Celestia and Sombra, and keeping the action confined to Sombra's castle and his battles with the evil versions of Celestia and Luna.
YMMV / My Little Pony: Friendship Is Magic (IDW) Issue 17 to 20