my interpretation (and a shallow close reading) of Event Horizon, arrived at while explaining the movie to Carolyn while she watched it, over the phone:
The main point is that the doctor who originally designed the ship was in-effect playing God, because he was trying to do something that is generally filed under should-not-be-possible. In accomplishing said act, he made the ship go somewhere it shouldn't have --> connected with him 'playing God' = so they saw God/the incomprhensible, as it were (re: the climax of The Gunslinger; literal translation of "Allahu akbar"). In and of such, through a grand extrapolation of 'humans fear that which they do not understand,' not only does the crew (and subsequent characters in the movie) go loco-in-the-braino, but the inanimate ship is also affected, later making a connection with it's designer to create horror movie fun.

Interestingly, there is also the twisty relationship that the audience has with the movie. Because the story is in effect being narrated by the main characters, they are generally thought to be reliable. But the trick is that as the movie progresses each of them becomes more and more unreliable, which either leads the audience to simply accept their perspectives as the reality of the movie, or try to recognize when they have become unreliable and then read between the lines, as it were, of their hallucinations.

All of that stuff about the nature of how the story is being told also plays into the personification-of-incomprehensibility that the ship has become after encountering it, as the longer the characters interact with it the more they take on its aspect, and thus produce the movie's effectiveness at scaring people.