Well that one is quite easy to test, and don't require a full mythbuster writeup. Sounds promising, but I havn't noticed it before.
So I started a campaign, spent all the money and went in the red, moved all my troops out of all my provinces and noted loyalty. Then I cheated to receive a million florins and noted province loyalty. Then I waited a turn to see if the treasury should be full at the beginning of the turn.
Result: Treasury has NO impact whatsoever on province loyalty.
/KotR
Bookmarks