Also, is there anything to cite about sensory connections in this place of your article?

Would sensory prosthetics be the kind of thing you're looking for? I can add some cites about those.

It seems that some medical operations could temporarily freeze inter-hemisphere communication. It is quite obvious that re-merging the brain should be simpler than coalescence. Did anyone find any human volounteers to tell about the feeling of that?

I don't think that this has been done.

Also, inter-hemisphere link could have some particular connection patterns which would be hard to reproduce - and without it maybe we need many more connections?

You say that cortex can shift functions around. But that probably uses changing some neurin connections, doesn't it? Can exocortex connections bee mutable? Do we expect the neurons directly on the end of connections to reroute the connections? Do we have any ground to expect or not expect locality problems?

I'm unsure about the answers to these, though they seem to me like problems that could be eventually overcome. I'll see if my coauthor has a comment - the neuroscience part was his domain of expertise, not mine.

And if brain could be quickly trained to overcome all that, is there any ground to expect anything below complete merge with uncontrolled rate after some threshold of learning to use the connection is passed?

Are you asking about a (natural brain)-(exocortex) merge, or a (natural brain & exocortex)-(another natural brain & exocortex) merge?

If there were enough connections between the exocortex and the natural brain, then yes, given enough time the exocortex would probably merge with the natural brain so as to become pretty completely a part of it. An uncontrollable rate seems to me unlikely - it takes a long time for a child's brain to develop to a mature state, and a large part of that development presumably involves various parts of the brain integrating with each other better - but again, the neuroscience side is not my domain of top expertise, so I might be mistaken about that.

As for one exocortex-equipped brain integrating with another, the extent to which that can happen obviously depends on the amount of connections / bandwidth available, and on whether the connections are maintained constantly or only for short periods.

A technical note - "Paths to Coalescence" chapter seems to discuss only one - exocortices. Why use plural in that case?

Good point. It was supposed to note that coalescence can be achieved by first "traditionally" uploading a mind and then directly creating connections between the emulated brains, or by an exocortex route. I'll clarify that or change the title.