I asked her why and she told me they didn't want people flying on any other carrier, because they lost money that way, so co.com would only show actual CO flights.
Somehow that just doesn't seem right. Very frustrating.
The other thing that has not been mentioned on this thread (besides the difficulty in booking codeshare flights) is the unfair way these "CO" flights are treated in regards to OP milage and EQMs. I found a very nice flight out of CAK to LAX via DTW and IAH. However, 2 flights were codeshares on NW metal. The flights were bookable through CO.com, but the CAK-DTW and DTW-IAH flights were on NW metal and were considered NW flights and had 50% milage and no points.

I think that if I buy it from CO and it has CO numbers, then it should be considered a CO product and get full EQM and milage. My little rant (moo)