Using C locale is useful when processing very large data files in a shell, e.g. on a server. For example, uniquing or set difference will work many times faster

Using C locale is useful when processing very large data files in a shell, e.g. on a server. For example, uniquing or set difference will work many times faster (and doesn't require the slow/fancy collation calculations). But yes, it's a good point, of course it shouldn't be used on your desktop globally or apps will break. I'll clarify that.