Not sure if this a bug or Working as Intended, but I thought I would comment. Near the end of one of the cultural branches, there is a tech called "Stellar Immigration" (at least for the Terrans, other races might call it something different). One of the things it unlocks is a Colony Only improvement that gives a 10% bonus to influence the colony generates and a +2 adjacency Influence bonus to all tiles around it. Should this really be 10% though? I get the +2 is kinda good, since all of the other Influence Improvements leading up to it are all +1. But the building immediately before this one is the Outreach Center which boosts Influence 50% and is +1 adjacency and can be built as many times as one wants. In fact, the lowest level Influence building is 25%/+1.
Unlike some of the other adjacency based improvements, this one can never be upgraded to something better. So, as I said, is this a bug, or, WaI?