Quote from PhanxIt's still horrible, though. The pre-3.2 autocompletion was perfect. I don't know why they'd change it, especially to something so awkward.
It's apparently a bug:
World of Warcraft Client Patch 3.2.0 Known Issues
The new name drop down feature has disabled the auto-fill feature
Presumably the auto-complete trying to fill in the second word of anything you type is also a bug, but there's no official mention of it I've seen.