I have always had food allergies but the onset of Menopause added a new one to my list - Soy! Holy Cow. Loving WDW and having a Soy Allergy is a bit tricky. I am glad that my allergy is only moderate and not severe.
WDW uses Soy A LOT as a dairy alternative. I suspect there are more lactose intolerant guests than Soy intolerant. The two restaurants I had to the hardest time in were O'Hana's (both Dinner and Breakfast) and Boma.
The best place was the Garden Grill. They use butter and not soy based margarine and or soy bean oil. I had no issues that I could tell at any Quick Service places but with only a moderate allergy I might not have noticed so much, depending on the food ordered/amount eaten.
In each restaurant the chefs had offerings that were delicious and soy free. They can accommodate a soy allergy. Just know that Soy is used widely in all of WDW.