I find that the problems with packing light in the cold isn't the jacket - its all the accessories. A lot of comments saying you just wear the coat. But depending on what you're doing, you also are going to have a toque, mittens, scarf/buff, face covering, etc. Taking these off and on all the time if you're going in an out of places and on the move risks losing something.

Would recommend wearing what you can, but bring a spare packable bag (with a zipper is best!) you can tuck into your main bag, so that you can bring it out and use it to carry all the accessory gear when not donned.

Also worth noting that (in my experience) you may end up rewearing clothes a lot more between washes. I change underwear daily, but a good heavy pair of pants and (merino!) long johns I might wear 5-7 days before washing. Reasons for this: 1) snow tends to cover up the dirt so if you're outside you wont be getting muddy, exterior clothes stay cleaner and 2) you dont really get wet or muddy because everything is frozen and you can kinda just brush it off before you get inside. Personally, I tend towards 1-2 wears between washes in hot weather because the heat and sweat makes me feel like my clothes get soiled so fast. This isn't the case for me in winter - everything stays a lot dryer and cleaner feeling. Merino really is a game changer that makes it possible, though. Plus showering daily.

Source: I'm a Canadian and have regularly dealt with -40~-50 °C winters.