Hello David
First of all, Merry Christmas and Happy New Year :D
Speaking of ThunderPlunger, I noticed an odd behaviour in the new "Validate email address" function.
I will describe it:
1) create a new card with name "Foo" and email address "foo@foo.org"
2) perform the validation of the entire address book - Foo will be detected as "suspect"
3) if I choose not to delete the card and dismiss the windows by pressing the OK button (note that the checkbox is NOT selected)

then it is displayed the confirmation dialog.

4) Pressing Ok will delete the card from the address book even if it was not marked to be deleted
Thunderbird 2.0.0.9 (X11/20071031) on Linux - Debian TestingBye

Simon