Not a muslim.
I would and have worn a scarf in the manner of a muslim woman. I have several that were gifted to me by a muslim former co-worker. I like to wear them traveling although I wear them over my shoulders and around my neck rather than over my hair. In the terminal and on airplanes they are just right for covering arms and body like a small light blanket to keep off the a/c or winter chill. The friend mentioned above invited me to her wedding. She explained beforehand that she very much wanted me to come, but to be aware that I (and all other women) would need to wear a scarf and wear a blouse or sweater that went to my wrists and slacks or a maxi length skirt and close toed shoes. I brought one of the scarves she had gifted me and there were aunties or grandma’s there that helped me get it on and wrapped with my hair properly hidden. It was not the sort that required a hidden face, just fully covered hair. Also I didn’t really notice anyone in the plain black that we tend to think of. It was very bright and colorful and the fabrics seemed very fancy.
While clearly I have and would do it out of respect at a friends special occasion, I do not think I would do it to “show support” in general.
But then I don’t wear the pink ribbon for breast cancer support or the gold ribbon for childhood cancer or orange for leukemia either. (And I had a child with leukemia.) I’m more inclined to give a recently diagnosed friend a small carry all with a small soft throw in her favorite color, Ziploc bags, hand lotion, peppermints s to take to chemo. I’d rather buy a lemonade from an Alex lemonade stand, take toys and books to the pediatric unit, give my lunch to the homeless person on the corner downtown, or make a donation in honor of someone than wear a ribbon, or scarf. I don’t have a problem with other people doing it. I see them and it does register that their lives have somehow been impacted by that cause. I think I am just more comfortable showing support by being a friend to the people impacted by those things as I encounter the people.