I'm using Word 2016, and in the Review tab when I select text and click New Comment, the document scrolls to an existing comment, rather than opening a new comment box pointing to the selected text.

Could this be because I don't always "post" comments? I'm not working with others, so I have no need to post comments.

I've tried repairing Word and rebooting, but neither helped.

Your assumption is correct. With the new comment interface, you have to "post" a comment before you can create a new one.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional