I can't confirm whether the General thing works, but I can say it sure doesn't seem like it. I have heard that one and I've heard the one about keeping them in the King's Stack or another General's stack and you won't get bad vices. In my experience, I have not seen either work.

I don't ever really seem to have generals who get alot of bad vices, until the Empire starts getting to big. It seems to become problematic when the Empire hits 30-40% of the total provences. It seems to get worse the larger it gets. It also seems hardcoded. One of the games way to counteract your advantage.

I do remember once while playing a Domination game, I made it a point to get rid of bad generals. I would strip them of titles and assign the titles to someone else. I started this just before you can get a minor victory. Pretty soon every general I had that was worth assigning to a Provence had at least one bad trait. The bad traits seemed to get worse as time progresses.

You can keep pruning your generals if its minor, but if you have a real large empire its going to spiral out of control.

I honestly don't know if there is any reliable way to stop it, but if anyone has something solid I'd love to know.