We generally do not have to write _foo. My suggestion was only for the few people who needs this feature, maybe to wrap an exotic lib without being willing to put much work in text mangling. That people can use full case sensitivity with underscores for VERY FEW identifiers and are happy. And we dont have to use their libs and we can have a style guide which says that one should try hard to avoid that style. I just remembered -- there may exist scientific libs that needs underscores and case sensitivity everywhere... May be very hard to rename all that properly, and may be hard for people coming from other languages and having used that libs for long time.
Personally I see some advantages in partial-casing -- so I do not have to remember if identifier is textView or textview. But of course disadvantages exists, for example not every text editor may be able to do style insensitive search.
