first of all, as someone who has bad self harm scars all up and down my left arm and was incredibly scared about wearing a short sleeve shirt, your coworkers nor managers/supervisors can do anything discriminatory. it counts as a disability so any rude comments, being treated differently, etc… can be reported.
despite this i know how scary it can be to show scars/fresh wounds and wearing an arm warmer (as long as it’s within the color patterns allowed) would be perfectly okay (just think about it the same way as someone wearing a wrist brace or a cast). if your SM or SSV doesn’t allow especially if you tell them why, i would report them to the ethics and compliance hotline. it’s literally just a long sleeve disconnected from your shirt.
as someone who’s also struggled so much with mental health and self harm, i really hope that everything goes okay <3 take care of yourself <33
also, i searched this sub and found
$1 post with a SSV saying it should be okay :))