I was annoyed at this too, and failed to find a decent automated solution anywhere on the web. So, I wrote a VSCode extension that watches the TextMate scopes wherever your active selection is, and if it detects a scope that contains comment, temporarily disables Copilot’s inline suggestions until your caret is anywhere without a scope that contains comment.
Or, in short, it makes Copilot get out of your way whenever you’re writing a comment, and lets it do its magic everywhere else.
Hopefully you can find some use for it as well.
https://marketplace.visualstudio.com/items?itemName=disable-copilot-comment-completions.disable-copilot-comment-completions