Why is this happening? The text is outlined and there is no stroke. (First image is before clicking 'unite', second image is after.)
Why would you use unite on these objects? They don't intersect in any meaningful way. But to the question try adding another anchor pooint to the upper version of the I before doing the unite and see if there is a difference.
Turn off "align to pixel grid"
So then pretend they intersect more; why is this happening?
Adding more anchor points did help a little bit, but it still distorts the shape(s).