A fellow player believes that there is a contradiction in the rules of The Multiverse. "You can't ignore another players actions" vs. "Your reality can have his actions not ever having occurred". I believe that this is not a contradiction, but how can this be?
First, we must make sure to understand three things;
This third concept is very important, because it is the crux of the issue. The very spirit of The Multiverse is such that we wouldn't have a roleplay without our willingness to collaborate, and moreover to offer our creations up for shaping by the often unexpected forces of other players' universes.
Your universe might not incorporate certain events as having happened, but the universe in which they are "ignored" is outside of the Multiverse, which is again defined as the set of all possible multiverses. That's the firm line drawn by the rules.
Now, as for the trust that the Game Master has in your participation, it is exactly the same type of trust that each player must exhibit for each of his fellow players: if we didn't count other players' actions as meaningful and having lasting impact on our own characters, we wouldn't have much of a roleplay, now would we?