okkkkaaayy. Make sense of this if you can!
I thought - there must be some way of disabling spelling suggestions through the touchbar. Went to system preferences -> keyboard -> customise control strip; no option to do so there. Searched internet and found that you can disable spelling suggestions in Apple's own Notes app. Thought, why not? Went there, did it, came back to Quiverapp and the problem is solved. I’m not getting word suggestions - but I couldnt care less; the flashing has stopped. Same is true of RStudio and ace in the browser. This is a repeatable “solution” even after reboot.
I only wish I’d figured this out earlier!
Cheers