Turning off email notifications about new comments in one certain file

In this case, I’d use Outlook email rules as a workaround. You could create a rule that, based on specific text in the subject line or the sender, automatically moves the notification emails to a folder of your choice. That way, you can keep your inbox clean specifically for notifications from those PowerPoint files without turning them off altogether. You can then either retain the emails in that folder for reference or periodically delete them afterwards if you don’t need to keep them.