Notes:

This seems to be the original source, the artist was not credited. There's a signature, but no one knows to whom it belongs. This comic is infamous for its esoteric punchline. The consensus of the meaning seems to be:

The guy replying Nay instead of No, made the server person feel like they are in medieval times and suddenly felt like they were a Knight (because it's one of medieval times' most recognisable representation)