Maybe it's my brain that's weird, but when I have a train of thought, and then read the auto-completion of my sentence, I forget what I was thinking and suddenly I can't think of anything other than the (usually incorrect) suggestion.
I feel the same from playing around with VSCode for a short while. All the extra "hints" everywhere, hovering stuff changes the look, the editor itself displaying fucking popups while I'm coding about updates or just "You could activate this extension now". No wonder people find it hard to focus when your code editor is literally trying to pull you out of focus at every turn.
The practical solution: Manually toggle it.
My favorite solution: Start the comment with a curse word.
Mostly I use comments for prompting code, so it's also not very useful for it to be auto-completing comments there.
The one time that it was incredible helpful was when I was writing JSDoc for a library. It was so fast at generating documentation and especially examples, it turned the task from something I would probably never have done due to tedium, to something I knocked over in 20 minutes.