Rated 4 out of 5 stars

Nice addon, but with Thunderbird 5 it causes signatures to malfunction - when composing new mail, if you change account in the "From" dropdown, the new signature is added underneath the old signature rather than replacing the signature. Disabling Stationery fixes the problem. I hope you can fix this soon.

This review is for a previous version of the add-on (0.7.3). 

Blame TB developers

You should blame TB developers for this problem.
Basically, TB code to update signature when identity change, always assume that signature is at end of message. If there is anything after signature, then this code fail to update sig properly, regardless of my extension.

When i got some time I will investigate how to fix it... But it may be problem, because original code is C++, and can not be overridden in extension.

Personally I prefer to embed signature in template, so I select signature by selecting template.