Plantain in both varieties, narrow and wide leaf are fine to feed piggies. It's on the safe list of forages from guinealynx. I think everyone should read the link I posted above. You can scroll the whole page and it has good links to what plants/weeds are poisonous.
i think so....my pig oreo sometimes has stomach problems if she eats too fast and we give her dandelion leaves and she poops it out. I think it does act as a laxative
Eek, my pigs are usually outside on a daily basis and our garden does have lots of dandelion greens. No wonder there is so much poop on the grass! I might have to put the pen on a patch where there is just regular grass and clover then.
On my lists it doesn't mention feeding in moderation. If your pigs have never had it, feed it in small quantities for a few days because it's a new food they have not had. If they do eat it, I don't think it would hurt for them to have a few leaves per day.