This same issue has been persistent even over multiple Windows 10 installs as well. Yes, I have uninstalled and re-installed Office 365 numerous times. I've checked through the MS Word options and I have not found anything there that stands out as the conflict. Yes, I have long-since disabled 'Hide mouse pointer while typing' in the mouse settings. Yes, I have obviously tried to fix this numerous times. I've been writing on Word for decades, and this is a problem that has hounded me for the last two years or so. I'd rather the mouse pointer doesn't disappear at all. As you could imagine, this is a massively annoying distraction that instantly derails train of thought. There is clearly some kind of conflict going on where something keeps trying to hide the mouse pointer while also making it reappear, particularly when pressing the SHIFT key.
Ok, this is the bane of my existence: my mouse pointer flickering while I type in Word.