Works better than wisestamp Rated 5 out of 5 stars

Install, first setup and usage is perfectly simple. Allows any html-tweaks in signature. small, fast, simple ... love it..switches completely reliable the signature in mail editor, when switch sending mailadress. love this feature!.
.
Tweak: AddIn does not show up, when writing mails "without formatting".
.
Contact of development, after bugreport is super-fast. All thumbs up!
.

This review is for a previous version of the add-on (1.15.1). 

Glad it's working now. Signature not showing up when in plain text format is as designed (as you put it), but I agree that it should give you an unformatted version of your signature when in plain text mode. I will plan to implement this.