[10C BUG] Does not correctly mark up mentions of old usernames in post content.html
See: https://10centuries.org/post/139675
schiffey was renamed to paulyhedral. The mentions record correctly records id, name (at the time, when mentioned), and current (post-rename), but the content.html doesn't have the usual span markup to flag as a mention, so it renders as plaintext.
We could correct for this in Macchiato by finding renamed users and ensuring their old names get marked as mentions.