Would you be able to track down on your end the user that who gave a feedback on this KB0013659. We could not find the user as it appears as a GUEST in Servicenow.
It is really very hard to track as the page is 'Public' meaning user need not to login. In this case it looks like user session got expired.
We would recommend, if you do not want guest user to give feedback then use below steps:
1. Go to Service Portal > Pages
2. Search for kb_article on the ID column
3. Open the kb_article record
4. Uncheck the Public