On the proper use of “hehe”…

My savvy friend whose use of “hehe” provoked all these questions said that “hehe” is one of his favorite words. He pronounces it “heh heh,” to indicate mild amusement “without having to resort to emoticons, LOLs, or ROTFLs.” He said that “haha” indicates “more serious amusement,” and adds extra “ha”s for “more serious mirth.” He wrote, “There is no such thing as “hehehe” in my vocab, though.”