For future reference, here is a thread about how to post code using code tags so that it gets formatted properly:
You may be over-using singletons here. Remember that if you declare something as “static”, there is really only one copy of that variable for all instances of that class. If you have a DialogueActivator on more than one character, then “DialogueActivator.instance” will point to the last character that set the “instance” variable (probably in Start). This may be why removing the other character causes the first character to behave correctly.