I emailed this to Zev and this is what he said
Charles's special ability says he may take two damage to attack the same character again. Does that mean you can attack twice on a turn with that ability, or that he can attack any number of times as long as he has the HP to spare? For example, if he has 2 damage, can he attack someone, take two damage to attack again, and then continue taking damage to keep attacking as long as he has health to spare? In that case, he could have as many as 4 attacks in a row if the rule is interpreted that way.
***Zev: I would say as long as he can pay for the ability he can keep doing it.