These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Karl, according to his Back Story, which includes losing much of his family to The Plague, befriending a local girl whose family suffered similarly, and falling in love, only for the girl to be crushed to death by a falling tree. Although it is later revealed that he was not as head-over-heels in love with her as everybody thought — which only made him feel more guilty about her death.
Jessica is heading this way, as in the second and third books, she has had a burning tree dropped on her and has had her face mauled by an enraged Treecat, respectively. Though given that she ended up getting a Treecat bondmate after the first incident (she was caught under the tree while saving him) and a boyfriend after the second (he came to her aid during the attack), she seems to be doing alright.