That's something a bit odd about Douglas Adams's reply. Arthur Dent isn't heroic, but he's the hapless protagonist. The protagonist doesn't have to be a hero. I'm not sure in what way he has "non-heroic heroism".
I also believe Adams was trying to point out, very gently, the same cultural difference I called out in the comment I replied to, i.e. that the American culture attaches certain expectations and connotations to the word "hero" not because they are intrinsic to it, but because of American bias.