I think if it's semantically a `control-label`, then anything that's a control label should have that class or not have that class. I think that's probably good principle of least surprise (and with markup, I think it's easy to ignore that kind of line noise). If it's semantically a `validatable-label` or whatever, then I'd use a class that makes sense. (Dunno if "validatable-label" is really what you'd want, that's just a shot in the dark.)