Why can't the SDE.Default version be edited when its privilege is set to Protected?
Answer
The default version is owned by the SDE user. When it is set to 'Protected', only the SDE user is able to edit. If a version is set to protected, only the owner of that version can edit it. This is separate from the owner of the data.
Note: The owner of a version and the owner of the data may not be the same user.