There’s a much simpler way to put it:
If someone has COVID-19 and wears a mask, it’s very unlikely they will spread it.
Even if you’re feeling fine, or you had an anti-bodies test, or you caught COVID-19 in the past, you should still wear a mask. There’s no telling when you may catch it and be contagious and a simple piece of cloth goes a long way to prevent other people from getting sick.