I had some strangers ask questions when I wore the pruple CCFA bracelet for a short time. Most just wanted to know why i wasn't wearing a yellow one. I stopped wearing it as I could not wear it at work (not comfortable with the questions it would bring up there) and I can't stand something on my wrist all day (as I am taking my watch off for the third time today).
I do have a Life is Crap shirt (the antithesis of the Life is Good line). It has a stick figure behind a stall door stall with the TP rolling away. People have laughed and then asked why a women would wear such a shirt. I proudly say that it was a Christmas gift from my husband who understands the nasty nature of having Crohn's disease. Then I let them ask from there. I will answer as many questions as they ask, but I try not to be too descriptive (unless they are rude of course)
I think it's great that people overheard your conversation....some folks may take better to understanding when they just happen to hear rather than "being educated".