> ext3 gives better behavior for people who don't code carefully, it's behavior is the gold standard
Its not even about coding carefully, doing the "correct" thing is not even possible in many of the use cases which are protected by the default ext3 behavior such as atomically updating a file from a program which is not in C such as a shell script. I learned, along with many admins, to use the atomic rename behavior to implement "safe" updates which may have been a misunderstanding at the time but can now be considered the new requirement.
At the time this issue was discovered with ext4 there was a frank exchange of ideas and the realization that the expected rename behavior is beneficial to overall reliability and we should make it work properly. I'd be interested in seeing this kind of thing handled at the VFS layer so that the behavior is consistant across all filesystems, that sounds like a great idea.