I don't require irony as a defense for something as unabashedly romantic and enjoyable as this, a twisty and devastatingly effective pulp drama. Irony might only serve if you don't see utter sincerity in the notion that selfless deeds might be a worthwhile corrective for past sins. Lovely.
Pretty damn weird, even by Sirk standards, and unfortunately the soapiness is relatively light on commentary. Still, it occupies a key place in his filmography, and it imparts the wisdom (just like Hitchcock's Vertigo) that if you're dealing with a narrative that's completely preposterous, just push everything—music, color, emotion—so far over the top that it becomes surrealist poetry.
In the Ross Hunter collabs at least, Sirk comes off as a very straightforward director. He places his actors simply and effectively, giving them lots of room and highlighting the setting without dividing the viewer's attention too much. What he achieves is a heightened legibility; he uses simple visual logic to evoke emotion as directly as possible.
Sirk's so-called ironic melodramatic swipes tend to leave me in two minds: simply lush soap operas or sly critiques of the hand that feeds them? Try as I might, one's reading tends to plump for the former. You can impose a retro-camp sensibility on these extravaganzas of insincerity (plenty of heavy underlining with celestial choirs and gaudy colour) , but don't dig too deeply - you might chip the varnish. Silly fun.