‘George Lucas Apparently Went “Apeshit” Over Harrison Ford’s Classic Line “I Know” From Empire’ - https://geektyrant.com/news/george-lucas-apparently-went-apeshit-over-harrison-fords-classic-line-i-know-from-empire-strikes-back - with quotes from Irvin Kershner and Harrison Ford (with video interview of Ford, by Jon Favreau).
That’s apparently from one of Irvin Kershner’s last interviews before his death.
To quote Kershner more fully:
[Irvin Kershner said:]
“George saw the first cut and said, “Wait a minute, wait a minute. That’s not the line in the script.” I said ““I love you, too’ was not Han Solo.” Han Solo was a rebel. George felt that the audience would laugh. And I said, that’s wonderful, he is probably going to his death for all they know. We sat in the room and he thought about it. He then asked me, “Did you shoot the line in the script?” I said yes. So we agreed that we would do two preview screenings once the film was cut and set to music with the line in and then with the line out. At the first preview in San Francisco, the house broke up after Han Solo said I know. When the film was over, people came up and said that is the most wonderful line and it worked. So George decided not to have the second screening.”
Apparently Lucas was worried the audience would laugh in a way that took them out of the movie. Fortunately people understood that it fit Ford’s character well and worked in the dramatic circumstances - so they laughed but thought it was excellent.
One thing that’s to Lucas’ credit IMO is that he’s always been very worried about what sort of things might break audience immersion.