I wondered the other day....what's the ruling on black arms/hands?
If a white guy paints his forearm black to stand in solidarity with black Americans by raising a "black power fist", is he helping or hurting?

Don't see the point. If i want to "stand in solidarity with black America" i'm sure my (Caucasian) power fist will do just fine, if a power fist, is the way one must go. Don't see much upside with black hands or arm but lots of potential downside. Maybe ask a few black people first before doing something that may be potentially problematic, regardless of your intentions. I assume there are many other ways to stand in solidarity if one truly cares. One thing we all know is that black face is an issue, so why even fuck with it? Imo seems so naive. In the end i would say it's hurting, because i feel it would potentially cause a distraction from the real issues you are trying to be in solidarity with.

The black fist has a historical significance I'm not sure a white fist conveys, but I do see the likelihood any attempted solidarity would be overshadowed by people's outrage at perceived racial appropriation.

A black glove seems more appropriate (although no idea if somehow it would be a bad idea) than a painted arm/hand, but still seems unnecessary as there are so many other ways of being supportive. Imo, It all seems very look at me, but context is everything.

pretty sure the best thing you can do is help the people who need to be heard get heard and not draw attention to yourself or be performative in your support [as a presumably white person]. i think painting your arm black would generally be perceived as performative and trying to steal the spotlight from those much more deserving. be like the white dude at the 1968 olympics: help create the space and then get out of the way.