Test and stabilize beforeInput in Collaboration Features

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There are a few things that must be tested and stabilized, for instance:

what happens if during a composition a collaborator did some formatting in the same paragraph?
what happens if during a composition a collaborator split the paragraph?
what happens if during a composition an auto embedding finishes (paste a link, start composition, link was embedded)?
does beforeInput go well with track changes?
- does a composition on top of beforeInput work as well?
what happens when the autocorrection kicks in (spell checker changes words as you type) and the Track Changes is on?
does spell check work correctly with Track Changes?
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(probably lots of cases)