I saw an old thread where a user previously posted, whom I know is frozen, but their name did not have the strikethrough on it. Their username is struck through inside of the hover box when you hover on their name. And when you go to their profile it says they're frozen.
I think frozen users names are supposed to have strikethrough on their username in the forums.
Hope this makes sense!
I think this issue is probably related to the user icon things not showing correctly on the forums since the switch. Like the purple for mini-mods and the black for , and the birthday cake icon.
Those all show up on the topic lists (for example here), but not in the user info section on actual posts.