They do this with coupes. It is style over substance and, yeah, it leads to
trouble with the rubber seals. They also have the window lower a bit before
closing and this adds to wear of the (already short-lived) window winder
mechanism. Sedans have proper framed windows, and also the under-designed
winder mechanisms.

BMW is a very strange company design/engineering wise.

Some things they do extremely well and intelligently (like the in-line six
gas engines and their diesels) and some things they do really, really
ineptly and almost criminally stupidly (sun-roofs, window mechanisms, water
pumps, E36/E46 rear shock supports).

It's like once in a while the adults leave the kids in charge of
design/engineering.

GRL

I got a ride in an E46 and noticed something funny about the windows.

The windows are kind of "stand alone"...they are not "in the frame" of
the door like on my old Japanese car.  When you close the door with
the window up, the top most part of the door IS the window...ie
there's no metal frame in which the window is enclosed.

I'm not sure why BMW does this.  I would think it maybe makes it look
sleeker...but you have to be careful to close the door from the actual
door and not the window.  In my Japanese car you can grab the top
corner of the door, right at roof level and it's metal.  In the BMW it
is the window itself.

Do they do this on sedans as well?

I'm just curious.  Sorry to belabor the point.