What are some strategies for dealing with feedback from multiple people? It can be difficult to sort through feedback on a paper/chapter when you have feedback from multiple collaborators. Sometimes collaborators might have a conflicting point of view, or making all of the improvements suggested by each would make the paper far too large.

What are some strategies on working through this feedback efficiently? Should you fully address each collaborator's comments one by one, attempt to merge all the comments together before editing the manuscript, or take some sort of hybrid approach?
It's a tricky question and I think the best strategy will ultimately vary from person to person. Nevertheless I have two concrete suggestions that has helped me a lot throughout the writing phases of my manuscripts and thesis. 


Get feedback in "rounds" instead of "continuously". When you have a version of the text on which you want feedback, send that to all involved parties at once. That prevents people commenting on each others suggestions and making a mess out of everything in the markup. 

Once you have feedback from multiple people, you can iteratively go through the feedback and add/ignore the changes on the master document. This is rather contradictory to the accept/reject change function on MS Word, but in my experience that's not really sustainable when you have a lot of cooks making a single soup.

After the "round" is done, remove most (if not all) markup from people, have a new version of the document with whatever else you want to add/remove. If more feedback is needed have a new round.
If there are co-authors who are more superior to you in the academic ladder and you are concerned about how to handle any contradictory/problematic comments, define one of your superiors to be the "alpha" and ask that persons help to try and settle disputes. It should be relatively easy in some fields where the last author usually has the ultimate responsibility for the project. 

Alternatively, if you have a supervisor/mentor who's gonna be a co-author but not the last; you can try to reason with that person to settle disputes. I have ended up in that situation where one of our co-authors decided to contradict with her own comments from before, and had these endless iterations of comments and changes. When I couldn't take it anymore, I talked to my supervisor and which point he took over the reigns and defined a new, final version prior to submission on which he asked all co-authors to have their final remarks. 


It might appear as a bit totalitarian solution, but at that point the alternative was me completely dropping the project based on this one co-authors unexplainable and unbearable behavior.