I loved everything about this movie apart from that goofy, unlikable moron. Such a shame that so many films of this period had to include 'comic' characters like this which inevitably kill the mood that they're trying to create.
He's not in it just because the movie needs a comic character. Jof is a simple man who is not brave or very smart. But he is not evil, wicked, crooked or malicious in any way either. Remember the scene in the tavern? Jof is tortured and disgraced because he is the only man who doesn't belong there. In those difficult times everyone expressed their black side, except truly pure - like Jof. Blessed with visions (Virgin Mary, Death, Dance Macabre) and guided and protected by Block and Jons, he and those like him and his family, are meant to survive this (and every other) dark period. Plus, Jof and Mia represent biblical Joseph and Maria and their son is Mikael - probably referring to archangel Michael.
He was one of my favorite characters, although really I liked all of them. The only one I didn't like was the perhaps most two dimensional character of the Blacksmith "Plog".
He was the odd man out; funny, silly, but knowing his talents -- which had little or nothing to do with war or "manly pursuits".
He loved his wife and child and they loved him in turn, even if his lovely wife did not always believe in his visions.
The seriousness he shows when he sees the knight and death playing chess seems very genuine. Enough so that when he demands they leave his wife does not argue.