Filesystems and case-insensitivity

This was basically my thinking too, I'm an amateur when it comes to filesystem/vfs design or kernel/user interface, it seems you could limit the scope of what the kernel tries to do to something reliably implementable, such as storing an encoding hint and validating the encoding on read/write, that would be useful for a reference implementation in userspace to handle normalization and locale and all the wooly corner cases that will probably require frequent patching, but I'm not sure that you could outlaw anything at the kernel interface except for strings that are not valid for the hinted encoding, or a very small blacklist of control characters. I don't know what the state of the art is in userspace, but it seems that a lot of these challenges have already been faced by web browsers, database engines and others, and it would make sense to me to re-use as much of that experience, or even implementations, as possible to build a consensus, conventions and a reference implementation for the libc's and others to use.