Flymake makes the margin unnecessarily wide.
Its 2 columns width creates too much empty space.
All this to accommodate 2 characters of "!!".
Whereas in the fridge it nicely fits into 1 column
with `flymake-double-exclamation-mark'.
It's possible to achieve the same for the margin case
by using 1-character wide indicator ‼ with

  `((error ,(if (char-displayable-p ?‼) "‼" "!!") compilation-error)