It seems that it's possible for multiple users to be editing a question at the same time.
When this happens, the user who submits the edit second has their change show up as if it were done entirely after the first person's edit, with no notification that the post has changed in the meantime. When the changes are generally the same but slightly different (say the first user fixed a few more things), then it looks like the second user is attempting to deface or reverse some of those changes.
For example, an edit that I recently suggested was probably ok based on the original, but definitely wrong based on the intervening edit: http://stackoverflow.com/review/suggested-edits/1313408
Can there be some system in place to prevent cases like this from accidentally occurring? Perhaps some in-your-face notification that "the post has been edited since you started your edit; please reload to see changes" or something?
I'm not sure if this is a bug in an existing feature that should handle cases like this, or just a missing feature...