Maurice updated the first post in this thread, and asked me to change the title to reflect the results of his survey.
I have had many cats eat foliage. I gave up on trying to start seeds indoors as my house cats always find a way to get to them and chow down all the tiny seedling foliage to nubs and have never been sick from it. My outdoor cats eat the seedling foliage too - but they also eat grass and chew on other young greenery of other plants. In the summer, they hang out under the daylily foliage, and are often seen chewing on the over hanging foliage tips. I've seen several of my indoor cats that managed to get up on my tables and get to various flowers I have brought inside and chew on the petals - daylilies included. I've never had any become ill to the point of being concerned about them, having them vomit or taking them to the vet. However, the outdoor garden cats might become sick and vomit and I don't know about it - but I don't think it is a problem for them.