Star Trek

[Moristans]

Was that due to a transporter issue or some other alien technology?

IIRC, it was a transporter issue due to something on the planet that he, Sulu, and some random red shirts had beamed down to. When he beamed back up, his signal was split into two Kirks, one with all his aggressive and impulsive emotions, and one with his more passive and considerate emotions.

The message was that neither one was the "real" Kirk. They both needed each other to function as the Kirk we knew.