Actually yes. And he was a ticklephile, and had a safeword with me. He actually started to cry and laugh at the same time (which is the weirdest thing a ler will ever hear). I stopped IMMEDIATELY (because as a ler, i don't take actual crying to be a good thing...regardless if he didn't use the safeword yet), but he told me to continue and soon he was back to just laughter. When he did finally say the safeword, he told me he was going through some hard times (he thought a tickling session would help), and the overstimulance of the tickling plus his situation caused him to cry. He said it was just what he needed, and he felt much better about the whole situation now that he got it out of his system. I actually heard of this before, but as a ler it was quite distressing...especially as I take care not to push people too far. But in this case, he just needed to let some shit out and tickling helped him to do so.
But in general, if i was tickling someone and he started to cry, I would stop immediately because that seems too non-consentual for me.