The article with an image spans two columns. Only the heading before a paragraph loses its margin. The form lights up when you tab into its field. The page stops scrolling while the dialog is open, and does not shift sideways.
article:has(img)
No image
Has an image, spans two
No image
h2:has(+ p)
A paragraph follows
So the heading has no margin under it.
A list follows
So the heading keeps its margin.
form:has(:focus-visible)
html:has(dialog:modal), while it is open this page does not scroll
Has an image, spans two