You mean a duvet cover or a doona? That is fairly common in many parts of the world. Americans are the one who like quilts and comforters mostly..
Yes, doona. I believe it's a Swedish word, in fact. It's a removable cover into which you can insert a blanket or quilt, making a sort of un-quilted comforter. I've seen them all over the world. It's very sensible to wrap the blanket or quilt up in something washable. Keeps the blanket clean.
But coming from the south, I also know the value of being able to throw off the blanket, bedspread and just sleep under the top sheet when it's a warm night. There are times when I've been overseas and it was too cool to sleep with nothing on me, but too warm to use their heavy sheet-encased comforters. So I've been known to rip the blanket out of the thing and just put the sheet sleeve over me! I'm always careful to stuff the blanket back into the thing the next morning.
EDIT TO ADD...
For those having trouble picturing what we're talking about, I've looked around and can't really find a photo. But imagine a pillowcase large enough cover a whole bed. Instead of putting a pillow in it, put a blanket in it. When you put it on the bed like a comforter, putting the open end at the foot of the bed. Guests can't get their face or hands around the blanket. All they touch is the outer sheet-like case, which you remove and wash after each guest, then put the blanket back in and put it on the bed.
I think it would be pretty easy to make one by taking two sheets and sewing them together on one end and both sides, then turn it inside out so the seams look good and slide a blanket in from the open end.
I think I'll use these in my place (on top of the top sheet and under the bed spread, in place of just a blanket). I've never been able to stand to have a hotel blanket touch my face in the night! This solves that problem.