No support.
1) Merchants use the pet auctions and can stock all their pets in there instead of using a rancher shop.
2) Most naturals have amazing names.
3) Some person could be desperate to sell their natural and not have any way to do it. Blocked from the SB and they don't like posting in forums (maybe they get ignored too much), auctions are their last option.
4) If we blocked off naturals from pet auctions then we should block off common eggs from item auctions. It makes just about as much sense to do so.
5) There are natural CS and seasonal creatu. They are valuable and blocking them from the auctions would cause problems.
I'm all for a filter, but 100% against blocking naturals in auctions.