Someone made an anti-gravity tag for things that float in a space that isn't necessarily outer space, then someone else used it for a Miku Append upload... it seemed to fit the image, so I tagged others as such.
I think anti-gravity covers it well enough; anti-gravity_hair seems too specific, given that just about all the posts in anti-gravity include the hair floating up. Actually floating would probably cover it.
Yeah, zero grav would mean that it isn't being affected by gravity and is floating in place, and anti grav would probably mean it's defying gravity by flying away without means of propulsion.
Right, and zero is what you're actually going to see in these images I'd imagine. There's generally not going to be a physical way to know if someone's hair is capable of negating and even reversing the effects of gravity. Just that it's floating. Anti-gravity seems to imply some technological assistance to me, while zero-gravity is an environmental condition.
floating_hair actually makes a ton of sense, it's descriptive and concise without making assumptions about gravity that might not be technically true in a scene.
I'd say it would come down to whether the hair was floating significantly more than the body. To pick some random examples from the tags mentioned earlier:
post #650075 has floating hair, but (assuming the thing behind Ren is sitting on the ground, which admittedly isn't clear) probably wouldn't involve floating in general.
It's not always clear-cut - post #676923 is floating, but opinions might differ on whether or not the hair is affected enough to get floating_hair too. Still, nothing's perfect.
Also, I don't know how we should approach dealing with the various gravity tags - though since we currently seem to have gravity, anti-gravity, zero_gravity, zero-g and zero_g, all separate and none with wiki pages, we should really do something. My feeling is that they're more about the environment, whereas floating is something the subject of a picture is doing - but that's just personal impression, and still doesn't address what to do with all the above-mentioned gravity tags.