Update. 7 tiles is too many. 5 may be the trigger point, or if you claim a tile within 3 tiles of CC of their city that there borders have not yet expanded to you. A city with niter 3 tiles from city where it was outside current city boundary, resulted in "too close humpt message" when placed a new city 5 tiles away and bought tile with niter as it was within my city 3 tiles limit. Interesting. If it's within the 3 tiles limit, then it would not be changeable, but if it's greater than 3, we should be able to change AI reaction to closer city placement without going to war.
