No Message Pane Sort 3.0.2
by thunderspeed
No Message Pane Sort prevents accidental resorting of the message pane by disabling mouse button clicks on the column headers, thus, locking the sorting order of your emails.
It is still possible to sort messages by ctrl-clicking the header.
About this Add-on
Then No Message Pane Sorting is the addon you've been waiting for. It disables mouse buttons clicks on the message pane headers and your message list stays sorted all the time. But just in case you do need to resort your messages: You can still do it by ctrl-clicking or command-clicking on the header.
Permissions: During installation, No Message Pane Sorting requests "full, unrestricted access to Thunderbird, and your computer". No Message Pane Sorting does not, in fact, accesses your files or anything on your computer outside of Thunderbird.
This is an issue with porting addons to the new Thunderbird mail extensions. Since mail extensions currently don't support everything addons such as No Message Pane Sorting need (and were able to do in old versions of Thunderbird), addons need to implement so-called experiments. Any addon that implements an experiment gets full unrestricted access to the user's computer including file system access. This was already the case in earlier Thunderbird versions even though it wasn't spellt out like that.
For more details see https://thunderbird.topicbox.com/groups/addons/Tc9a1303c15d0444d-M43d93470680298ba6c1f9aa0/permissions