- “Having a Lufthansa airplane filled with 300 passengers holding tickets on LH999 is no different from from having the same flight with 100 passengers holding UA tickets, another 100 holding CO tickets and 100 with LH tickets.” and “Having a CO flight connect with a LH flight is no different than having a CO flight connect with the same LH flight but with a CO designation on the ticket.”

No different for whom? Think about it this way: Lufthansa does not offer flights from Central America to Europe. Continental does! Passengers can now buy tickets through LH and fly on CO aircraft to Houston (as an example) and continue on LH.
Of course those flights have existed before and could be bought seperately. But have you ever checked, what those so-called fully interlineable fares cost??? Only thanks to the so misleading code-sharing is it now possible to buy those tickets with 1 airline (and you choose to buy on LH, UA, AC or CO and their revenue will be shared accordingly).

And this also answers the part: “The level of service is the same. The level of codesharing misinformation is multiplied.”
Cause service is not only the quality of the on-board Crew but also the service of network range, frequency of flights, capacity (!) and connectivity!

“However, when all options are considered, travel times are almost always similar.”
This may hold true for you (I am assuming you are US-American) cause you have had a well established domestic network. Have you ever tried flying from the Middle East to South-America???
I do think it makes a MAJOR difference if now you can choose to connect once, twice or even three times! Don’t you?

I fully agree with you on the “By having antitrust immunity for marketing, pricing and route structure, the alliances can coordinate pricing better than ever.”
Though this is only of advantage to the consumer because prices become more transparent, 4 airlines will offer exactly the same price and trust me: airlines cannot afford not to be competitive these days. And with AA+BA, KL+AF and now NW+DL kicking in, competition is existent.

So before shouting, start thinking! Not every JV (and we are not even talking about a classical JV here) automatically creates monopolies that harm the consumer…