Google Docs has a suggestions feature where you can have you or other people add suggestions that you could put in the final product. That would be a great Word feature
Herbert Perez commented
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Right now, users need edit access to the document before they can add comments.
This is not satisfactory because users can inadvertently edit the document which means the review cycle needs to be repeated.
Ideally read only users should be able to read and comment on the document without being able to modify it.
Adobe provide such a feature with PDF Review but we are invested in O365 and would like to use the Microsoft products that integrate properly.
Something that we have in Google Docs, is the ability to have someone suggest something
Daniel L. commented
Add more granular versioning in Word Online. It should be more like Google Docs where you can edit a page as a group and see exactly which edits were made by who when
id like it if you added an edit only mode so you can have a document as a read only an edit mode + a new comment only mode