I'm sure many of us have seen our characters gain prestige from doing odd things that one wouldn't suspect would cause gain. If I recall correctly, one character gained prestige from persistently looting
Most recently, I received the following for persistently building wall segments!
Your engineers are now busy adding another block of fortifications.
Your continual performances have finally paid off. Your prestige rises one point.
If you've had a similar thing, it would be interesting to hear about it here!