“I never said that it did. The Mishna Berurah also doesn’t say that you can’t wear black nail polish :)”
That is why I said that I don’t think it’s assur to wear black nail polish.
You seemed to be saying that it’s assur to not wear braids, since there are Rishonim and Achronim who say so, and you told me (or tznius? I thought you meant me but realized afterwards you may have meant tznius) I should ask a sheilah about whether it’s assur not to wear braids. Since it’s not in the Mishna Berurah and I’ve never heard any contemporary poseik say it’s a problem, I see no reason to even ask.
btw, since it’s in the Rishonim and Achronim and yet the Mishna Berurah doesn’t mention it, it seems that he doesn’t hold that way. This is especially true since he does talk about hair covering, so he would have said something there if he considered it to be the halacha. On the other hand, since the Rishonim and Achronim don’t talk about nail polish to my knowledge and the Mishna Berurah doesn’t talk about nail polish at all, we have no way to know if he would have considered it assur. So there is actually more of a reason to say that nail polish could be assur.