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.
Suddenly fully invoking his charisma abilities when taking over from Colon as well.
Could be Character Development as well — he was raised in a culture that doesn't really grasp irony and puts great store by contracts and laws, but at this point he's spent years working with Vimes (who manages to at least hold his own against Vetinari most of the time) and living with Angua (who's got a lot in common with Vimes, personality wise). He's grown up.
Fridge Brilliance: Vimes and Sybil both privately hold the opinion that Carrot and Angua's relationship is under strain because of their concerns about not being able to have children, or producing a Complete Monster if they do. This is never brought up in either Carrot's or Angua's point of view sections, and it's made pretty clear that the problem actually stem from a completely unrelated source note Angua's anxieties that she will become more like her family and eventually turn on her non-werewolf friends, and that she can't be accepted by other species because she's neither a human nor a wolf. While it doesn't make much sense to apply this reasoning to Carrot and Angua, it actually makes complete sense for Vimes and Sybil to think like this, since it's a projection of their own situation: Vimes is afraid that they've missed their chance to have children by marrying in middle age; and Sybil is afraid because she's just discovered that she's pregnant with her first child, and is unsure of how Vimes will react, or the effect it will have on her health.