I’m actually unsure if it is ironic or not. But, it can’t be irony, not on a sign… and not here.
TACK FÖR ATT NI INTE DRAR IGEN GRINDEN
THANK YOU FOR NOT PULLING THE GATE SHUT
Never seen anything quite like it before. The eternal negation inte/not on the other hand is more than familiar. There’re so many questions.
Please see: The signs series.