If you open a knowledge article and mark it as Not Helpful or give it a low rating it opens a dialog window. If you select 'No Thanks' or click outside the window without choosing any options or setting any values, it still creates a task record for the knowledge article. Can this be disabled?
The task is created when the article is marked as not helpful or when a low-star rating is given. That's the moment it determined negative feedback is given. The additional popup window allows you give additional details, but this is in addition to the feedback. You can see this in the wording of the popup message: Thank you for the feedback, please provide additional details. This is the expected behaviour.
As a workaround you could consider introducing a Business Rule to delete the task record (or set it to completed) if Reason=Other and Description contains 'was marked helpful'. This would indicate someone clicked on the button but didn't fill in the form.