Comment 128 for bug 151162

Not sure it's worse but it seems not what we are used to.
All mail clients I know (and also Thunderbird) create a new file with a full copy of the attachment. That seems to create a link to the attachment. If wonder what happens if one edits the saved attachment (let's say it's a .doc on .odt) but I bet that it's just a bug, not the intended behavior.