How we cite our quotes: (Chapter.Paragraph) Note that chapters aren't numbered, so need to be numbered manually, 1 to 14.
Quote #4
So the computer existed independently of me; that meant that the Station and its inhabitants really existed too. (4.103)
Kelvin has proved to himself that he is not just making everything up. He would maybe be disappointed to learn that Stanislaw Lem is making everything up, though, so even if he gets out of his head, he's still stuck in Lem's.
Quote #5
"… I saw you weren't there, I was very frightened, and…" (7.73)
Rheya explains why she Hulked out and bashed a door down when Kelvin left her alone. Remember, Rheya (the real Rheya) killed herself when Kelvin left her. It's not entirely clear if she is desperate not to be alone because that's how Solaris visitors work, or if it's part of her personality because it's part of her personality.
Quote #6
"We are the cause of our own sufferings. The polytheres behave strictly as a kind of amplifier of our own thoughts." (9.45)
It's not aliens that torture you, it's your own thoughts. The reason the visitors are bad news is because the scientists aren't talking to anyone else; they're trapped in their own heads. They need to get a Facebook account and meet other people, obviously.