to blue and rabbi:
You missed the point. The point was that any undefined halacha (e.g. “bright” or “long hair”) is not a halacha at all. Halachos are specific (e.g. a succah higher than 20 Amos is Passul), even if we do not know what those specifics (an Amah) are. If bright would be a halacha, then the chachomim would give a shiur as to what is bright and what is not, or they would have said a Tefach is OK for hair, more is too long, and we would be arguing over what is a tefach!
In this case (tznius), there is halacha, minhag hamedina (which halacha says to follow if their standards are better in certain cases, as not to be look worse than the general population (don’t know if that applies today, when you can’t even look outside!)), and minhag (which is a personal thing). They are different issues. The original poster just seems to have gotten them confused.