See the costume this avatar is wearing. Is this really a hat? It says the user has no hats. Bug bit?
Yeah, it is the Hello World hat, which some google research seems to mean the user scored a +1 on their first question. It indeed seems to be a bug.
Even if a user's profile does not show the Winter Bash snowflake, you can see their hats by appending
#winter-bash to the URL for their profile.