@DisillutionedJW:
To me it is clear that the verse is saying Judah and the listed gentile nations will serve the king of Babylon for 70 years (even if the desolation of Jerusalem was not proclaimed to last for 70 years).
Right. From this verse you can't say the 70 years applied to the desolation. You can say Jerusalem will become a desolation, but the 70 years attaches to servitude. It applies to servitude of many nations. What does it mean when you have a bunch of nations serving a single nation? Some sort of empire. It's Babylonian rule. Seventy years FOR Babylon.
About the commentaries you cite. A commentary is just that - someone commenting. And that's fine, but in the end, if the commentary winds its way around tortured logic just to switch seventy years of servitude of many nations into 'a period of time when one nation lost its sovereignty' - thereby extending the date beyond v12 to when the Jews got back and started to rebuild, then that commentary wouldn't hold anymore weight to me than the WT commentaries.
I don't go for the "someone - somewhere agreed with me, therefore true" argument. (Not that you are using that logic)
That being said, that commentary begins the 70 years at 606, the date they choose for the first Exile, long before Jerusalem's destruction. Fine - its defining the "desolation" referred to in v18 as more of a soft desolation, like a vassal or servitude. Ummkay. But that still doesn't mean Judah will be "desolate in the sense of servitude/vassal" for 70 years because the 70 years applies to the nations. Why start it at the first Exile of Judah when Neb had been marching around making vassals of other nations round about for years prior? Why reduce 'nations' to 'nation'?
Why not stick to 539 as the end of the 70 years, as verse 12 says, back up to around 609 when he was conquering Assyria, and call it a day?