Finn was not present, obviously, when Rey kissed Kylo Ren, and I started wondering what on earth (/Tatooine) he made of the whole situation.
REY: Hey Finn Kylo Ren turned good again and then we fought my evil grandfather who wanted me to rule the galaxy as Empress and then all the Jedi came to me and I died and Kylo saved me with Force Healing and gave his life to me and I snogged him then he died.
FINN: …. okay cool?
But in all seriousness I think Finn learning the details of Rey vs Palpatine would make a pretty good fanfic. IF I can do it! So far I have one paragraph:
At that moment Finn hated Kylo Ren, and Ben Solo, more than he had ever hated anything. More than Captain Phasma, more than General Hux, more even than the people who had wrenched him away from his parents as a toddler. And then, after a moment, he didn’t. Maybe that was the Force. Finn wasn’t sure he liked the idea of it messing with his emotions.
& the ending:
“I love you.”
“I love you, too.”