Thunderbird adds the ">" prefix to each sentence of quote when you make a reply message. And, Thunderbird adds "[" and "]" to the subject when you make a forward message.
You cannot control this action from settings. Threfore, the ReFwdFormatter add-on solves the problem!
How to Install in Thunderbird:
1. Right-click the link below and choose "Save Link As..." to download and save the file to your hard disk.
2. In Mozilla Thunderbird, open Add-ons from the Tools menu.
3. Click the Install button, and locate/select the file you downloaded and click "OK".
· Mozilla Thunderbird
What's New in This Release: [ read full changelog ]
· Support Thunderbird 3.x.