`enable_forwarded_emails` doesn't behave like conventional email forwarding

Inline forwarded messages are getting trimmed away, with both quote and create_replies modes enabled.

Any suggestions?

Original message (some headers removed):

From: Jeffrey Lastname <jeff@myemail.us>
To: test-cat@example.org
Subject: Fwd: Thank you for your support!
X-Mailer: MailMate (1.14r5745)
Content-Type: text/plain; format=flowed

Some really long sample text.

Forwarded message:

> From: Donations Team <giving@example2.org>
> To: jeff@myemail.us
> Subject: Thank you for your support!
>
> Dear Jeffrey,
>
> Our heartfelt thanks for your donation to Example Project, 
> especially now. Together we will write the future.

Message in the forum board (same for both modes):

Some really long sample text.

Forwarded message: