I think it is fairly common. I never really noticed that I had spotting around O time until I started charting while TTC DD2. The month that I conceived her I spotted for 3 days around O and then a day or two around implantion, I am not sure if maybe it has to do with the size of the egg that was released, I remember reading that somewhere.

I cannot see your cycle, does the spotting occur around your O time?