A mailextension for Thunderbird that prevents accidental message sorting.
Do you accidentally resort your messages because your mouse click hits the message pane header instead of the top most message?
Then NOMPSORT MX is the addon you've been looking 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.
Head over to addons.thunderbird.net to find the current version. Development releases might be available earlier in the Releases section on GitHub.