The KB mentioned (TECH205753) was resolved in 10.0.2. Here is the solution from the KB:
The issue with original message attachments failing to contain Subject or Recipient information has been addressed with the SMG v10.0.2 release.
This is otherwise an expected and correct behavior for email messages that cannot be cleanly restructured to accomodate the annotation.
So, the issue that was resolved was that subject and recipient information was being lost when the original message was attached. This has been corrected as of 10.0.2 and this information will not be lost when the message is attached.
Otherwsie, as Ben said, it is expected that the original message will be attached to preserve it and make sure that the disclaimer is seen before the message is viewed and neither are corrupted by differing character sets or content-types.