When someone sends you a .doc file or images that are attached, when you reply done they (and others CCed) won't be able to see the appropriate history. If it is a word .doc or an image; open it and copy and paste the text/image into the footer. Don't leave it as an attachment.
Warning: iPhones strip inline images
If someone has replied to a beautifully crafted email (with inline images) with their iPhone, it will now be a clipped plain text email.
So in such a case, you will want to skip that email and go back to the last HTML email and past in the extra response. For clarity add something like:
"(fixed history to put back images - caused by Adam's iPhone)"