They Might Not Allow You To Forget
Every breakup is not as definitive as the one before it. Sometimes, after going their separate ways for a while, partners finally get back together, and everything turns out okay in the end. However, this does not necessarily imply that your ex-partner has forgotten about the breakup in the first place.
They are not going to forget about it easily, as evidenced by the fact that this person can attest to it, and it is possible that they will not. However, it is heartening to note that now that everything has been addressed, they are able to laugh and joke about a difficult period in their relationship. This bodes well for the future of their partnership.