There’s more.
The episode with Cornwell is the real giveaway. When it becomes obvious that she and Lorca have a past, he is uncomfortable as hell. He knows that interacting with this old flame is potential doom for him. The writers set up some other character defect to distract us from the truth. We are presented with the PTSD motive that, once Cornwell detects it, will result in the loss of his command as a bait and switch excuse. It’s really quite brilliant writing, actually. I totally fell for it at the time.
So did my wife. Her fan paranoia was totally geeking on the Loq/Tyler switch. She was distracted by its more obvious outlines and so did not see the bigger, subtler tale – just as she was intended to be. Clever; very clever.
The problem is that stuff like this amounts to “Save the Cheerleader; Save the World” or, better still, R+L=J. Like a GRRM novel, once you tip your audience off that forensic analysis is required, it becomes a lot harder to surprise the audience in subsequent seasons. You only get to be a virgin once.
In Lithe, the episode with Admiral Cornwell:
* Cornwell notices old scars on his back that appear odd to her; they were not there before.;
* Cornwell brings up a meteor shower that she and Lorca saw years ago when they were much younger and Lorca changes the subject instantly;
* Cornwell remarks that Lorca “seems to be a different person” and;
* Of course, there is the phaser behind-the-back incident with Saru.
At the end of Episode 9, Lorca does something on the computer and punches it in. That results in the Discovery making its way to the Mirror Mirror Universe. That was not an accident, It was the end product of all of Lorca’s schemes. He did it to finally get home. He even says so “Let’s go home”. At the end of all of these jumps - to parallel universes that Lorca blatantly states the Spore Drive may be able to access, Lorca types something in to the computer. There is an entry about the jump that briefly appears on screen that says: “OVERRIDE, LORCA, G. SPORE JUMP 133— UNKNOWN.” And poof. Mirror Mirror Universe - here we go.
Lastly, and perhaps not so obviously, we have the idea of his photosensitive eyes and his refusal to get them treated. Something is there that Lorca does not want anyone to examine closely. The injury is explained as a consequence of the attack on the Buran. The injury – or genetic defect? – is probably much older to be explained by an event as recent as the Buran. Lorca doesn’t want Starfleet Medical to go there and find the source - or to detect the age - of that injury/defect.
In the past few hours since I’ve gone down this rabbit hole, I have now entirely sold myself on it. Ruthless Captain Gabriel Lorca, sole survivor of the USS Buran is not some departure from Starfleet that cavalierly breaks 50 years of Star Trek canon. The Captain Lorca we have come to know has been from the Mirror Mirror Universe the whole damned time.