A family of Microsoft word processing software products for creating web, email, and print documents.
Sorry - that was a typo. 16.51 is what I have.
I believe I see the problem... Microsoft is in the process of constructing the Editor feature for Mac Word. However, they seem to be doing it by slipping in unfinished, fragmented bits & pieces to limited groups of users for testing purposes. There have been a number of proofing-related issues over the past several weeks. The Editor component is fully functional in Word for Windows, Word Online & the Online web app but they haven't yet got it right in Mac Word. BTW: This isn't being done by any one specific update. Each change is being sneaked in surreptitiously via the back door & very well may disappear in the same manner or be replaced by some other anomaly.
Unfortunately there is nothing that can be done at the User end other than sending negative Feedback via the Help> Feedback feature.[or the Help Improve Office icon at the right end of a document title bar]. The mor users who complaining & the louder they scream the more likely Microsoft will hear.