Just a comment, I’m pretty sure this feature has to do with something similar teased for AOE4. We’ve already seen that several of the DLC civilization bonuses have shown up in AOE4 (Sicilian and Delhi Sultanate units being able to build defensive buildings, Burgundian and English farms generating gold, etc.), and as I talked about in this post, Deconstructing Age of Empires IV Fan Preview Video [Piece by Piece] - #16 by AlyoshaVonDiego, it seems likely that neutral markets will make an appearance in the upcoming title, too. The hints that something similar could happen in AOE2 just makes the inclusion of neutral markets in AOE4 seem all the more plausible to me, when considering all of the other features that have been carried over.