We were always told not to swallow watermelon seeds as they'd end up in your appendix. May be some truth to that.
I thought the watermelon seeds have a mild toxin, which causes some to throw up when they have consumed crushed watermelon seeds, mostly in juice.
Note though now-a-days watermelons of the seedless variety are common.
I was told not to eat watermolon seeds because watermelons would start growing out my ears. You obviously didn't hear what I was being told, because you have watermelons growing out your ears.
My dad used to tell me that, and it scared the crap out of me. I was thinking the same thing (about some truth to it) when I read through this article. Guess I will forward it to Dad so he can see that he was possibly right!