I guess, as with any disease, nutritional information changes constantly. Coffee is a perfect example. One day it's bad for you, the next it's good in moderation. Over the past few years I have noticed there's some confusion regarding kelp/seaweed and soy products for a person with hypothyroidism and hashimoto's disease.
Here is what I know. The reason some doctors suggest eating kelp/seaweed is for the iodine. In very small amounts it can be beneficial for the thyroid. BUT, it's not something that any person should eat unless they are tested for iodine deficiency. Too much iodine is bad for the thyroid also. So if you're taking a supplement with iodine in it, please make sure you've been tested FIRST and found to be iodine deficient. In Canada and the United States, iodine is in our food. Table salt, fertilizers on the foods the animals eat, fresh produce. Chances are, we are getting too much to begin with, so it's probably best to avoid it until tests show it's needed. Below is a website you can check out with a little bit of information.
Soy products. Wow. Soy is in almost everything that has been manufactured. Even dog food. It is extremely versatile as something I call a "fake food". Fake foods to me, are foods that pretend to be something they are not. Soy is not meat, although through manufacturing it can look like chicken nuggets or ground beef. There has always been the information available that soy blocks thyroid production. Which in turn leads to so many other health problems. I don't have enough space in this blog to discuss them all. Even people without thyroid problems shouldn't be eating soy. So for a hashimoto's patient to eat soy, it would be extremely detrimental. Below is a website that has more information.
Now, I know you can always find something on the internet to say exactly what you want it to say. I'm sure if you looked hard enough, you'd find a website proving pigs can fly. So if you have doubts, even if you've read all there is to read on the internet about these foods, perhaps those doubts should hold some weight in your decision to consume soy and iodine. Perhaps you should not throw caution to the wind about them. Perhaps taking the chance it won't hurt you, will actually hurt you. And why would you take that chance?