LooksLikeHTML decided by the first character alone, so a markdown post
opening with a hero <img>, a <div> or a comment was served as raw
markdown and its first edit stored ## and ** markers as HTML in both
columns. Load now serves such a value as HTML only when content_html is
empty or missing, or holds that same HTML (the value or SanitizeHTML of
it, white space at the ends ignored); otherwise it serves content_html.