Is there any way (or add-on) to include the full reply headers (To: From: etc fields) when replying in Thunderbird?
By default it only places a "On %date%, %user% wrote".
The reply header format is driven by reply_header_* preferences.
However I was never able to figure out where the user defined format had to be defined at.
I recommend not bothering with preferences at all and instead using SmartTemplate - it is a great extension that does its job well.
There is a great page in the Mozilla KB about all that: