I think the branches only merge if they're similar enough to merge by random chance. That means no meaningful transfer of memories, per the "no communication theorem" for quantum entanglement.
Why would the universe be more likely to send me memories from one of my distant branches, than from another currently-living person? I don't think telepathy exists in either case.
Have you ever woken up from a dream where you're sure you've forgotten 90% of it, but remember the portions most relevant to your reality?
No information has to be transfered in these cross-universe death/wake-ups. You can simply wake up with no recollection of the dream.
I'm not suggesting that branches containing separate information ever merge. I think my language was imprecise. I'm suggesting that one's perception of self-awareness and consciousness merges. The consciousness you have access to leaps to the next available branch.
I would not be so quick to say, with such certainty, that I know to what degree any organism can experience the division of universes.
I believe I've died many times in many timelines and wake up each day in one I'm still alive in... sometimes with fading memories of the one I just left. (Obviously, there's no way to prove or disprove this, so I normally don't trouble to tell people; they'll either find it out for themselves or I'm wrong, just a broken set of neurons seeking some higher order in its own chaos).