Oh FUCK YOU, Microsoft, what fresh hell is this? This just started turning up today. Whenever I start or click into a different paragraph. And there's apparently no way to turn off the "alert" bug in 365 for MacOS.
Welp. Unless I can learn to ignore it, this may be the thing that pushes me over the edge into using Open Office. (Is that the current best open replacement for Word?)
Okay! Strong consensus points to LibreOffice. Which is probably what my brain was reaching for, but got the other one because it was closer to the edge of the shelf.
Thank you all! Will definitely look into this.
Excellent: Confirmation that LibreOffice .docx & .xlsx outputs are viable!