Of course. So everyone can decide wether to use it or not.
Or even switch this on at some point in the boot sequence
Currently the linux kernel doesn't have an interface for this. But I think it is important to do this within the kernel so no malicious program can bypass it.
I agree, I think having a CONFIGURABLE option in the kernel where admins can decide "what is allowed" would be a big step forward. (1) Enable requiring UTF-8 encoding, and (2) list what bytes are allowed/forbidden at the beginning, the middle, and the end. Then you could have a local policy like "UTF-8 only", "no control chars", "no dash at beginning", and "no space at the end".