Should I care? If I am designing a system that requires only a full legal name...then it depends on the law of the target region. If it's for almost anything else...I'm not going to waste my time unless there are more than a few complaints.

My entire point here is that if it's really important to the system being designed, that the correct answer will occur to you naturally. Honestly, if we design a system that requires full legal names and we don't look into the laws of the target region, then we're probably not too bright.