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.
It also happens with the some of the more recent Portraits DLC. The artist changed, and a big part of the community thinks the art comes off in poorer quality than before. Some people (keeping up with the recent fad in the forums of making petitions for everything) are petitioning the mods to redo the facepacks. The issue often descends into a Flame War.
Even Better Sequel: The original game, while it had its fans, was definitely a flawed game, with a Troubled Production and quite a lot of bugs. Crusader Kings II, on the other hand, has received by far the smoothest launch of any Paradox game to date, and received almost universal acclaim from the fans. Expansions like Sword of Islam and Legacy of Rome have only served to make it even better.
Fridge Brilliance: Have you ever noticed how courtiers of a dynasty, when not influenced by the player, tend to 'not' marry after some two generations or so of sitting on their hands as courtiers, and subsequently ending that particular branch of the family? Well, what if it's the way of the game representing that that particular branch pretty much became plebeians, and thus the records have been lost to history due to unimportance?
This goes hand in hand with the mechanic of inviting (read: creating new) nobles to your court. They didn't just form out of thin air. They were always around, but when invited they become a part of recorded history.
They seems to be a divergence between a character's physical traits relating to their appearance (specifically the "Attractive" and "Ugly" traits), until you realise that you are looking at their portraits. Portraitswhich can be embellished.
Goddamned Bats: The Old Gods adds raiders who will plunder your territory, then flee back onto their longboats before your army can get to them.
Good Bad Bugs: The demo for the sequel restricted play to only four characters. However, almost imminently players found out they could play whichever character they wanted by picking a character from the demo list, then quickly clicking on a province on the map before the game loads - and play as the ruler of said province.
They also found out that the demo doesn't end twenty years later but specifically in 1086 and that if you set the start date at 0AD you could get 1086 years of playtime out of the demo. However, this screws up the triggers.