There is (or there will be) additional spacing between fields when they flip to the vertical display that should make it clearer. Our forms (and form row styled elements) have flipped to a vertical arrangement since older versions of XF1 and I don't think there's been an issue with that.
Ah, I see, perhaps it could do with the grey line break between the custom field and the text part of the post? As per the resource page.
It would help give a little differentiation between the two parts of the post.