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.
Harsher in Hindsight - While telling Jake about the horrific history of alternate!2011, Harry mentions that "four of the Japanese islands are gone" due to the Earth's increasing seismic instability. This may or may not count as a "Funny Aneurysm" Moment, since most of the book was completed by the time of the 2011 Tohoku earthquake, but the actual quake is later mentioned in the story. Speaking of the Japanese disaster, also worth mentioning is how in the alternate timeline a nuclear meltdown in Vermont irradiates much of New England.
Hilarious in Hindsight: In The Langoliers, it's mentioned that because of the way the time rip works in it, you can't, say, go back and stop the Kennedy assassination. And then this book gets made..
To be fair, Langoliers described The Past as a set being cleared, so traveling into the past just moves you backstage. Jake moves to a different point in time, so basically on the same stage just an earlier scene.
Jerkass Woobie - Oswald is depicted as a somewhat sympathetic character.
The Woobie - Harry Dunning. Not only does his essay move Jake to tears (and help inspire his journey), the universe shafts him in all three timelines; in the normal one his dad murders his entire family and cripples him (Harry) for life, in the next one he's killed in Vietnam, and in the final one he's left paraplegic in the war.