Warm winter jackets: what is truly warm? What are down jackets filled with?

Dear users, dear authors,
which winter jacket / coat / jackets do you like best? Do you like down jackets? What are they actually filled with?

A down jacket can only be called that if it’s lined with down, and as such, these jackets are a total no-go for me—I react to anything with fur or feathers by getting puffy eyes and having trouble breathing.
How warm a jacket should or must be always depends on the person wearing it—how warm do I like it, or at what point does it get too hot and become uncomfortable?

Best regards, Inge

Yes, as someone with allergies, down is off-limits for me, but there are plenty of jackets lined with thick fleece, so that works.
However, I’ve noticed that in our part of the world (at least here in the Cologne area), you don’t really need very thick clothing. Here, the “layering” approach makes more sense, because it often gets much warmer during the day than you might fear in the morning, and you can count the frosty days on one hand anyway.

Well, when I sew jackets, I line them with Alpine fleece or, if I have them, old baby blankets. That makes them nice and warm and cozy. But I don’t sew down jackets either. 

I’m bumping this thread up again.

In general, I like down jackets, but I don’t really like that with my last one, down kept poking through the fabric. Depending on which sweater I was wearing, it would end up “decorated” with down 🫣
This winter, I bought a new one with a quilted filling. It keeps me just as warm, and my sweaters stay clean.