The father-in-law becoming a born-again Christian and becoming much more abrasive and rude to his family and friends over time. Several commenters question whether the guy's change of attitude might be indicative of a health issue — like a brain tumor or illness — and not a case of Belief Makes You Stupid. Or was he just always an asshole, but his new religion gave him an outlet and "appropriate" targets?
The comments in this story seem divided over whether the dad's submitter was Crazy Awesome for navigating out of a state about to get hit by a massive snowstorm (and only just barely keeping ahead of said snowstorm), or if he was just crazy for risking crashing his car and injuring himself and his family in rapidly deteriorating weather conditions just to not end up stranded in a hotel in Wyoming for Christmas (it's mentioned that semis are already losing control and toppling over).
This mother, guilt-tripping the cashier about her grief (about which the cashier had no way of knowing), just to punish the cashier for making small talk.
This submitter treats their toddler brother being focused on his food — tightly gripping a pack of chips while asleep; taking food off of an aunt's plate or flat-out prying 'his' chip out of her mouth to eat it himself — as funny and cute moments. Comments points out that this is disgusting behavior, and worry about this unhealthy obsession with food.
In addition, many balk at the idea of a rule that unattended snacks are fair game for anyone to sample—this is heavily implied to be the reason behind the brother's food obsession, and if nothing else it explains two of the three moments (gripping the chip bag so no-one can steal any while he's sleeping, and taking back a chip that his aunt took from his bag while he wasn't paying attention). The most generous commenters say that it's ok if it's all fun and games between family members in on the joke and old enough to take it, but someone that young should have been exempted from the start.
Designated Villain: This mother is treated as unreasonable for not listening to the OP's request to just power-cycle the router to fix a connection issue. However, the connection failures are stated to have been happening several times a week, indicating a more deep-rooted issue that a simple reboot can't fix. This makes the mother's reluctance to perform a treatment just to fix a symptom more understandable.