Feature 2: E3L7 has E3's secret exit and has a silver door but no silver key. E4L3 has the next (E4's) secret exit and has a silver key but no silver door.
Feature 3: E4L5 has three exit elevators that cannot be used (they are blocked by barrels). The next level, E4L6, has three fake entry point walls.
Feature 4: Again involving E4L5, it contains an initial two blocked elevators. Then, excluding obvious ones like E2L2, E3L8, etc., it contains the only and only absolutely mandatory secret in the entire game. Maybe the two elevators (one is the correct one, of course) behind the locked doors are 'secret' elevators (except not really)?
Coincidences, or not? And can you think of any other eerie things that *just might* have been done on purpose?