By default, Microsoft Entourage automatically adds a signature at the very bottom of an email thread. I reply to dozens of emails every day and for a long time I used to cut the signature from the bottom and paste it to the correct place.
You might ask yourself how come I kept doing this. Very simple, I just could not find the right setting under the Preferences pane that would change the behavior. There is also no setting related to the positioning of the signature under the “Signatures”window to address this.
I finally found the time and did some online research and was able find the answer. I figured others could benefit from this tip as well. So, here it is. To get Entourage automatically add the signature at the top of the reply/forward, make sure you have the following setting:

BTW, Gmail used to have the same problem but recently added a fix to the Gmail Lab called Signature tweaks. Hard to imagine this has not become a standard feature of every mail client.
You can create several signatures but only one can be set as the default.
So if you set a “main” signature you like to use at the beginning of every new email thread and you get a response to which you wish to reply, there is no way to have a “secondary” automatic signature on your replies only? If this is not possible, this is a major pain with Entourage that wasn't an issue in Outlook.
As far as I know, there is no way to define a signiture for compose and a
different one for reply.
The closest thing to that is adding more than one signature to the pool of
potentially used signatures by checking the “Random” checkbox next to each
signature (accessed from Tools… Signatures). I am not sure how useful this
feature is though.
Thank you for this! I have been searching the web and could not find an answer to this question anywhere. I greatly appreciate your efforts to dig deeper and share the knowledge!
Thank you thank you thank you!!!! I am a recently converted Mac person and this bug in Entourage has been driving me nuts! Today was breaking point, I finally decided to research and fix it (no help from Entourage help button)!!!. Your email was the best guidance of all! I have also had a giggle at all the replies below, and it's a relief to know that I am not the only one. Well done to everyone and most importantly Jay, who has just saved my Mac's life, I did consider throwing it out the window! Has anyone worked out how to delete the reply after the first instance (i.e. it is good to insert a signature on a new email, but if I am corresponding back and forwards with someone it is a pain to have it on every reply).
Thank you very much for this useful information!