I just found the new extension (as of Sept. 2011) "editemailsubject" (must be typed as written, without blanks, in Thunderbird's extensions search). It allows to edit the subject displayed in the mailbox window while preserving the subject in the message header. Exactly what I was looking for.
I just found the new extension (as of Sept. 2011) "editemailsubject" (must be typed as written, without blanks, in Thunderbird's extensions search). It allows to edit the subject displayed in the mailbox window while preserving the subject in the message header. Exactly what I was looking for.