So far, I have not addressed any sort of conflict or compromise between competing realities.  It's simple enough to just claim that two realities fail to have sufficient overlap to generate any sort of conflict or demand a compromise, as there's pretty much always some difference, however minute.  But this is not useful.  Demanding 100% of details match, or even 99% of details matching, this is just an academic quibbling over influence, simulacrum, and etc.   Well, let's be more interesting, starting here.
	We could stick with the example of the falling tree from section one, or we could use something like a movie that is interpreted differently between multiple viewers.  Perhaps the movie example would work better, as it more easily escapes hard science (and so we do not have our time wasted by literalists).  Let's say you and I both watch a movie, and that afterwards, we speak of what the future holds for the characters of the movie.  This demands two major factors, I think:  imagination and understanding.  
	Understanding is knowing how the particular setting of the movie operates, along with an understanding of all the characters.  There is of course going to be a lot of unspoken knowledge drawn upon here, as you and I probably have very different views on human psychology, social dynamics, and other such things - but we have to let this go unless we are going to have a lengthy discussion about some movie I just made up (and most people would balk at such a discussion in the first place, so I don't believe I am being lazy here).
	Imagination, here, I am meaning more one's ability to process knowledge entirely within their mind.  It's pretty closely tied to understanding, but a strong imagination can sort of make up for poor understanding, and vice versa.  When we try to determine the future of characters from this movie we watched, we both must literally imagine one or more speculative futures.
	So let's say that we both come to drastically different conclusions of what the future for those characters holds.  This is essentially the divergence of one reality into two different realities.  The two realities occupy the same space, though, so the divergence creates a conflict that must resolve.  That space is the imagined future of the movie.  While the future is theoretically uncertain, it is lazy to bring that up as a final point, so we are going to dismiss it and demand some certainty - this is the future of a fiction, after all, I don't think it is unreasonable to affirm a future that has no method of hard verification.   We have our own intuitive systems for verifying such things.  It is basically the "Does this make sense?" test.  When we tell each other our imagined futures, the listener automatically will consider and determine if it makes sense.  They will reference their own understanding, imagination, but also some subtler cues like the storytelling abilities of the speaker, or personal bias between us.
	I think it's a fair assumption that any product of our imagination and understandings will make sense to us...let's go ahead and say that "making sense" is a numerical trait by percentage, and that anything we come up with, will be 100%.  A 0% would be something that has some fundamental contradiction to us, and sounds like nonsense.  Well, even though we both shared our 100% ideas with each other, we are not left with two 100s.  We have something more like one 100 and one 90; we each are confident in our own imaginings, but find the other to be lacking in some way.  Okay.  But we are not content to just write the other person off as wrong, so we discuss our ideas.  Gradually, that 90 becomes a 95 as we absorb additional data, and the additional data brings our 100 down to a 99.  While we could probably discuss it long enough to reach equality, we probably will stop after becoming bored.  Once that 100 stops being 100, anyway, it is evidence that the idea we once had full confidence in is no longer representative of our understanding and imagination; we must re-answer the question to re-attain that 100.  And on so doing, we can share our answers and influence one another in a cycle moving towards an equilibrium (likely never reaching it), but it's a little less boring than just direct discussion.
	Well, what's the point, right?  Check this out:  the summary affirmation of a reality is the total sum of "does this make sense" by all observers.  If your numbers perfectly reflect my numbers, then we maintain a conflict.  This is not realistic!  It is much more realistic for one of us to gain a stronger affirmation than the other.  That is the process of compromise between two competing realities, even though it's been represented as a compromise between two observers.  I would like to assert that competing realities naturally move towards compromise, but the rate at which they do so is entirely dependent upon subjective affirmations of observers (not merely how many observers observe the idea, but how much each observer cares).  The state of reality in absence of observation is the only true "objective reality", but it is unobservable and so not really able to be discussed without continuously destroying the topic we chase.
	Of course, just because something is not realistic, does not mean it never happens.  If we maintain a perfect conflict between our views, then the next step is to introduce additional observers and/or additional data.  Every such addition greatly decreases the likelihood of a maintained conflict.  I don't want to get into it in this section, but one can also create their own observers to help tip the scales.
	I would like to point out that this has nothing to do with the truth.  This is about the affirmation and denial of a reality.  A reality being denied is not the same as it being false.  By contrast, a true reality is not necessarily one that is affirmed.  The ever-present philosophical pursuit of Truth is not here, and does not belong here.
	One more thing.  Realities still compete with each other, even without mutual observers clearly existing, because the observer is only the source of affirmation and denial.  Affirmation and denial change the.."strength" of existence, so to speak.  But they are not used to turn nothing into something or something into nothing.  An idea (and by extension, a reality) may exist with zero observers - no, I will go as far as to say that infinity ideas and realities exist, even if no one has observed them.