So I got to thinkin… What if… there was an adverse effect to the two redeemed gals that served as a bit of a “scar”?…
 
Elf ears was the solution. I also thought of doing slitted eyes but only realized that halfway though the drawing sooooo oh well.
 
Aaaaanyway. My headcanon is just that! the two gals being a bit self conscious about their forever mark of their mistakes, only to find out later on that they, as partners, find the trait adorable when the other gets embarrassed or blushes and they droop a little like that.
 
Sunset has an easier time hiding her trait seeing as she has more wavy and droopy air but at times she finds she just can’t hide it.  
Twilight has a bit harder time hiding her ears but seeing as there are some folks out there with naturally occurring ears that are pointed out, people aren’t as assuming as with Sunset.
 
The two have a bit of a rough time after their initial magic power trips and find that they now have slitted eyes and pointed ears to remind them of their past. Though, as thy come to accept their mistakes, they also come to accept their marks. Though the once sneaky and best liar in Equinn Valley, Sunset Shimmer, turned into the most readable person along side Twilight. The eyes and ears give it away when she reacts.
 
The two find each other’s traits adorable, however. Whenever Twilight finds herself overly embarrassed or blushing, twirling her hair around her finger and such, if you look over at Sunset, you can often find her own elf like ears facing down with a Goofy smile on her face to match. Although the two are oblivious about each other’s feelings, It’s often hard to miss.