No, not sure at all. I didn’t know that was a problem with down. I have no experience with it. Since Rapha promote their down jacket for cycling I reckoned that you can use it for that. If it’s only for after the ride I’d obviously not care as much about fit and potential water resistance.
Down absorbs water, you're not supposed to sweat in down. For example, when you're mountaineering, when warmth really matters, your biggest enemy is sweat: your layers are going to include down because its insulating properties are dope, but if you start sweating and stop (part of the climb when doing belays), you very quickly question your life choices.
And so, you dont wear down on a bike, because you sweat on it. Once down is wet, if you're in the wild, you're as good as fucked.
Primaloft and other synthetic fibers that cost much less than down are better suited for sweaty situations because they absorb moisture less, dry faster, and continue to perform somehow even as they get wet.
For bikepacking, i would very much worry about moisture management and the insulation properties of my garment when wet. Being cold, wet and miserable in the evening because your gear is wrong should be avoided if at all possible.
Rapha selling down jackets can make as much sense as canada goose selling down jackets, or moncler: Rapha is a luxury brand, down is expensive, natural, and popular: they get it to sell you that jacket for a pretty penny, & it doesn't mean you should camp with it.
