Thanks for this. I'm such a chronic lurker that even though I've browsed HN for years I only today made an account, so needless to say this really scratches my itch. I really hate that instagram popup.
Scrolled down someone's random page with this extension and the browser tab froze and stopped accepting input (mouse & keyboard). Without any technical explanation I would say this is just removing the overlay and does not accomplish what it states.
Interesting, does it happen every time you try it or just sometimes?
I tried to locate the issue and think I found it. I updated the extension to version 0.0.2. Could you please check if the new version helps with the issue you had?