Definitely down. That way you don’t stab yourself when you’re adding or removing other silverware. Plus the dirtiest part of the fork is closest to the strongest part of the water jet = better cleaning.
According to the instructions for my dishwasher, forks up & knifes down. Except for the steak knifes which fall through so now put the knifes in the back section. No stabbing problems. Almost everything always comes out clean.