Author: tom[at]compton.nu
[Added to the original trac issue at 2.58am, Friday, 19th June 2009]

I'm not sure this makes sense at all - we are sending the comment (and we have no idea if the comment is in the same language as the diary entry) to a user so any text we add is in that user's preferred language.

It sounds like the real bug is that you're saying it is using the commenter's language not the diary entry writer's languages, but I can't see why - I'll have to look at it when I'm back home next week.

Author: kaerast
[Added to the original trac issue at 9.11am, Friday, 19th June 2009]

Yes that's it, the notification email is being sent using the commenter's language and not the diary entry writer's language.

Author: edgemaster
[Added to the original trac issue at 8.36pm, Saturday, 20th June 2009]

(In [16027]) Force locale on subject translation for diary comment notifications, since the sending user's locale is not that of recipient.
It is assumed that sender locale is that of recipient for the rest of the emails, which is fine, since the sender is the recipient.
The bodies are accounted for correctly by common_headers and the monkeypatching of ActionMailer.
(references #1968)

Author: edgemaster
[Added to the original trac issue at 8.42pm, Saturday, 20th June 2009]

(In [16028]) Contrary to what the previous commit message said, we do actually have more cases of user A triggering mail to user B.
(references #1968)

Author: Edgemaster
[Added to the original trac issue at 8.44pm, Saturday, 20th June 2009]

So, I think the case here is that the email body is being translated, but not the subject.

Can the original reporter check to see if this fixes the issue he's reporting once the fix is deployed?

Author: Edgemaster
[Added to the original trac issue at 8.46pm, Saturday, 20th June 2009]

One more clarification of what was happening:

Email body being translated into recipient's language.

Email subject being translated into triggering user's language.

The latter has been fixed to translate into recipient's language.