User blog comment:DiegoAnime3000/Black is for Polarity/@comment-15145664-20140110234404/@comment-3146930-20140111202434

I keep calling it the White-Glyph, but it is the blue one we are talking about. I keep thinking white because it is the opposite of black and because it was how it is used in the trailer.

Anyway to clear things up, Weiss' Blue and Black glyphs aren't polarity, because in the series that is the ability to control and move metals and all the forces needed to do so. However Weiss' Glyphs are a completely different Semblance and work completely differently. If for example her Black-Glyph was polarity and could only pull, then Weiss herself wouldn't be stuck to it, only her sword and all the metal objects close by. Inversely if her Blue-Glyph could only push, then her sword and all other metal objects would be repelled. Weiss herself however would be completely unaffected as she isn't made of metal. That is why her Glyphs aren't polarity.

However, if her Glyphs were able to control gravity, it would make more sense. The Blue-Glyphs are able to push things away depending on the power Weiss puts in, but the Black-Glyphs increase gravity and pull things in. Using the fight with the Boarbatusk as an example, Weiss makes a Glyph in the air and jumps up to it and it turns black. It pulls her onto it and Weiss stays there until it turns Blue. This is like how Gravity constantly pulls you back to Earth, except Weiss made an artificial Gravity platform that held her in place. Then when the Glyph turns Blue again, it pushes her away with great force, like anti-gravity.

Of course I'm basically just saying that the Blue-Glyph pushes things away from it and the Black-Glyph pulls things in; but these glyphs pull/push any object that touches them. If the Black-Glyph was polarity like you are suggesting, it would only effect metal, not people.