I recently came across this answer and found that the user has been deleted:
Generally, the deleted users will be displayed like this:
Why does that alone has a different view? A deleted user without a user id / name?
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I am not exactly sure, but this may be a possibility:
The post is from 2008. In those early days, a lot of work had to be done on the system. Maybe, at the time the user was deleted, there wasn't an automated process to purge or reset display names of deleted users. Jeff said the user himself had to change his display name before a user should request deletion. Maybe the user name and all his information has just been reset / purged from the database.
It is also possible the user had some invisible characters as his display name.
This happens when both OwnerUserId and OwnerDisplayName fields are null in the Posts table.
There are currently 2313 such posts on Stack Overflow, as can be seen in this query.
As you can see, it's not only for very old posts, latest one being from 2011.
Can't know the reason how both fields are null, just stating the facts which explain this outcome, and hopefully this will help the team find the root cause and fix it. (e.g. applying the ID back)