Fem seeds are female plants that are purposefully hermied in order to create feminized seeds. Not a plant that hermied on it's own, that's just bad genetics then.
hermie polen on another female is a way they make fem seeds but you can get bad genes that way, another way is using colloidal silver.
Hermie pollinating itself, I would think that would just be shit genes witha high chance of hermie in those seeds. Althou I am likely wrong about that, its just a guess.
it's done all the time... they will be female seeds. if the plant is a natural hermie and not stress induced then there is more chance of those beans being herms themselves.
I've grown plenty of S1 beans and never seen a hermie... buy them from large breeders though who are supposed experts and i've seen lots of hermies. DNA one of the biggest offenders.
basically if it happens through stress and the plant pollinates itself those beans will all be S1, and will all be female... if it's a natural hermie you have more chance of getting hermie beans. a higher percentage of the beans will be herm's.