I have been rated negative by a user I have never even conversed with.

Please advise.

Maybe ask the person kindly why they did that? I accidentally rated someone negative when viewing this site on an iPad. The device is pretty good at preventing unintentional button presses but they do happen.

Cheers. Yep, that's likely what has happened.
I have had another one today! They've messaged me to say it was an accident.