I've always been a quick tap when it comes to my ankles because I messed both of them up by playing on torn cartilage and sprains in football in high-school, so now there's so much scar tissue and floating cartilage there that if I did the necessary surgery, I would be out of work for upwards of 9 months, and I can't afford that. It's actually part of the reason I started bjj, because I can't play basketball or even touch football like I want to (going all-out). I've told guys in my class about it so they try to take it easy on my ankles, as well as take advantage of my lack of stand-up ability (little bastards).
But to answer the question, I've tapped guys via head in arm control maybe 3 times, once I got a tap via forearm-in-neck whilst in mount. That guy got shit from me for like a month.