Board Thread:General Discussion/@comment-24491127-20160222124014/@comment-27701762-20160223003517

I'm not sure what you mean by "regular Pacifist route." Do you mean a Neutral route in which you don't kill anyone? The Neutral ending does not change aside from the phone call you receive from Sans and the advice you receive from Flowey, so there is no need to differentiate between different Neutral routes.

Assuming that's what you meant, there is not really any indication of what actually happens to the main character. All we see is the character walk through a doorway. There is as much reason to believe that the character is trapped somewhere, whether it is in the Underground, or in a sort of pocket dimension, or somewhere else, as there is to believe that they escaped through the barrier. If we take the "character is trapped" route, then there's no need to explain the issue, as the barrier hasn't been crossed.

I prefer this interpretation, since it is a much cleaner explanation of the problems, though I know there are certainly other people who prefer the interpretation of the character escaping.