Your comment may have accidentally got caught by WP's Akismet spam filter. It's also possible that the person has blacklisted you to prevent you from commenting. It may also be an issue with your browser settings—specifically, cross-site tracking and/or third-party cookies, as this is what lets someone's site recognize that you're signed into WordPress. If you’re using Safari, go to the "Safari" menu > “Preferences” > “Privacy” tab. “Prevent cross-site tracking” needs to be unchecked. In Chrome, go to the "Chrome" menu > “Preferences” > scroll down to the “Privacy and security settings” and click on “Site Settings” then “Cookies and site data”. “Block third-party cookies” has to be turned off.