https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98014
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- !$omp parallel & !$omp num_threads(4) & !$omp !comment !$omp end parallel end is also rejected. And in !$omp parallel & !$omp num_threads(4) & !$omp&!comment !$omp end parallel end we treat that !$omp& as the last continuation line and accept it, but as the & is the last non-blank character before comment, shouldn't that mean a continuation is required?
