Can you select a seat on code share DL/AF flight?
 

Given my experience this week, apparently not. I had booked with Delta BOS - CDG. AF had no record of my reservation nor seat request. They told me their computers cannot talk to Delta's. The aisle seat DL had confirmed months ago was not available and AF stuck me deep in the middle of a row. Also was told that if AF is forced to bump someone, DL ticket holders are selected first.
Is this the norm with code sharing?

I flew SFO-CDG last week and ran into the same problem. Delta's site had my itinerary, but when it linked me to AF's site to check-in/change seats it would only throw an error. So, by the time I checked in at the airport, I had exactly 1 seat to choose from. Although, everything about that plane felt like it should have been decommissioned a decade ago so I'm not sure any seat was particularly "good".

Anyone have experience with the KLM SFO-AMS flight? That was the alternative that I wish I had taken.

Maybe this is something new...I flew DL DCA-BOS then AF BOS-CDG and didn't have a single problem. I asked DL to give me the AF record locator then went to the AF website and got my seat assignments quite easily.

This is the key. Trying to do it with the DL PNR won't get you anywhere.