Dont worry about him he,s just an old fart.
he probably thinks we are talking about teflon ...lol
loads and loads of our plant use modern day plastics like delrin as bushes for pedals and linkages etc and they are out in the sh@t and elements all the time, modern plastics are a bit more stable nowadays.
so use a good quality one.
As for the pivotif you are going to use a bolt use a shouldered bolt so the delrin is not running on threads.
cheers les g