+++ This bug was initially created as a clone of Bug #1169996 +++ Please take "Bug 1169996 - Changing the spell check language in the message subject of a recycled message via right-click changes the composition language preference" in THUNDERBIRD_38_VERBRANCH The patch is there, it's been reviewed, pending check-in by a code sheriff. This is (somewhat) important: In bug 967494 we changed the handling of the dictionary selection. Sadly later we discovered that the implementation had two problems: Bug 1168945 and bug 1169996. Both have to do with recycled windows which obviously weren't tested enough before. I've only noticed the problems when using TB38 beta for real. The other bug and this bug can lead to really confusing situations for the user, so IMHO they are important in order not to shed bad light onto TB. Kent, I know you hate last minute changes, but it's better to squash a bug before it's released than to face the support issues and fix it later.
mozilla repos took bug for gecko 40 and 41, THUNDERBIRD_38_VERBRANCH in mozilla-esr38