In general a great idea, since this feature is not available by default in Thunderbird - wonder why! However, it doesn't seem to work as expected in the following situations.
a) When I reply to an email the plug-in does not add the signature, even though I have the settings configured per instructions.
b) If you manage multiple accounts, and let's say you are in account A, click compose new email, realize you want to send from account B, change it in the compose window; the add signature no longer inserts the signature.
I will say that I searched high-and-low for a way to get rid of the "--" that is inserted by default by Thunderbird. I found a solution and implemented it and I am wondering if that has something to do with my issues. Any thoughts/ideas are welcome.