You may not have to show up at your status listing. In order to do that, you have to notify your lawyer or public defender and have them appear. If you are a Jane or John Doe, you have to give up your name and social security number if you want your lawyer to appear on your behalf. R2K Legal is encouraging people to appear anyway, so they can make decisions about their case and support others. Also, it would be good to have as many people as possible at the Friday and Saturday night solidarity meetings.
Judges expect order in the courtroom, and they expect people to stand when they enter the courtroom.
There may be a local court rule forbidding T-shirts with political messages. The typical wardrobe for a defendant ranges from suits to dress-casual to working clothes. For people who do not have fancy clothes and would like them, Philly activists will probably stockpile a choice of clothing. The decision of what to wear and how to act is a political decision that has implications for one's own case and for others' cases. Seemingly disrespectful clothes or behavior can bother a judge and hurt one's own case, but comrades who do want to be noticed will not be as dangerously positioned if they are joined by many others.