Jobe 1, When you say, "Unfortunately, there are other uneducated shoppers waiting in line behind you who won't know the difference between a real Dover sole and a cheaper fish masquerading as one and will buy it anyway.", you make it sound like the general public is just an ignorant bunch. That may be, however, the information you listed on this fish is pretty much the same info available on Wikipedia, and you may as well include the majority of the posters to this thread, because most of them have responded with a shoulder shrug and some secondary information, at best. I include myself among those that know little more than what was posted on Wikipedia. Although, I did know it probably 20 years before Wikipedia existed.
I was a chef through the 80's and into the 90's, and apparently, none of the info floating around has changed since then. I asked this question to various fish mongers with whom I did business and they all said the same thing, more or less, as is found on Wikipedia now. The only sole is the one from the Dover-ish area. Nearly everything we get here is some variety of flounder that has been renamed. Another very common version of this scam, (It is a scam) is on the West Coast with "Snapper," or "Red Snapper." It's rare to see real Red Snapper here on the West Coast. What is usually called Snapper, is really Pacific Rock Cod. I remember one fish market in my relatively small town selling fillets of "Rock Cod" displayed with the skin side down. A couple feet away in the case from that was fillets of "Snapper" displayed with the skin side up, for a dollar more per pound. (Both were skinless) It was the exact same fish! This same store has been busted numerous times for weights and measures violations and some sanitation violations. Fortunately, they finally went out of business a few months ago after about 4 decades of ripping the public off. The "Dover Sole/flounder scam" and the "Red snapper/pacific rock cod scam" is common in California.