One thing I never quite understood about city maintenance (having read that article a couple times, albeit not quite recently), is how to understand (and whether there really is) an actual, concrete formula for it which is usable by the player when deciding when and where to settle another city.
Having played this game so much and understanding the rules of thumb about the ICN and the factors involved generally, I usually can gauge pretty well how much of a total maintenance hit each marginal city will inflict, but it would be cool to know the literal way that that's calculated, since IIRC the author of that guide just inductively plotted a somewhat irregular looking data pattern without actually discovering the inner workings of the mechanic itself. My first thought is that it is spaghetti code which only a few people who worked on the original development were privy to and have now long since forgotten.
For all practical purposes at my level of play, having an intuitive feel for the general factors involved is good enough, but I'd imagine at a certain level, being able to actually calculate a specific number for the impact of each new city (especially when we do know this for things like trade route yield, cottage development time, etc., and the counterracting factors) would make a pretty significant difference in the quality of one's game.