Consider the following sequence of events:
- Users A and B both start editing a post.
- User A submits his edit.
- User B submits his edit.
User B's edit cannot be submitted:
User A already edited the body of this post; your edit must be more substantive to override the current edit.
However, when user B does not have edit privileges, this is not happening: user B can submit a suggested edit based on the original version of the post, blissfully unaware of user A's concurrent edit.
Example: B suggested an edit at 15:54:36 which is clearly from the original version of the post even though A made an edit at 15:54:06. The suggested edit diff is shown from version 2, even though A made his suggestion from version 1.
In this case, B should have been prevented from submitting an edit and told to edit from the latest version of the post.
I've seen that happen countless times on SO, but it's often difficult to trace at SO's fast pace where multiple edits often muddy the waters. Here's a case with a clear timeline.