The reason you see corn in your poop when you eat corn is because the corn is not easily digested by our stomachs.
Corn is not easily digestible because corn has an outer shell of a compound called cellulose and our bodies and stomachs do not contain enzymes that specifically break down cellulose.
So that leftover cellulose is basically what you see in your poop.
The body can digest part of the corn but not all of it.
Corn is very healthy for you even though the body cannot digest most of the corn.
It's perfectly normal to have corn in your poop even when your bodies digestive system is working properly.
Just like you can have Jalapeno Pepper seeds in your poop which makes your anus burn when you poop after eating Jalapeno Peppers.