Can Thunderbird be configured to display the full newsgroup names?

Here's an example of how Thunderbird shortens the names:

Answer

I don't know whether this still works in the current version (don't have a TB installed on this machine), but it used to be that you go into the about:config (Edit -> Preferences -> Advanced -> General -> Config Editor), then search for the line

mail.server.default.abbreviate 

And change it to false. And you should be good.