When Tilly kicks Michael in the face, the cut on Michael's neck has disappeared.
Kovich explains that Georgiou is dying because she's recently traveled in time, and the molecules in her body fight to return to the Mirror Universe. However, 98% of all atoms in a human body are replaced each year from food, drink, and air - so before long not a single atom present in her body would've been a mirror atom.
Lt. Cmdr. Yor's uniform lacks rank insignia.
Ensign Tilly asks Captain Saru if she should debrief the admiral. As the admiral is her superior officer, she would 'brief' him or he would 'debrief' her, not the other way around.