Rated 4 out of 5 stars

It works great and easy to use.
Here are some pointers:
- doesn't link to the account signatures, you need to recreate them manually and might create issues on the long-run
- The signatures are added at the end of the email, so if you are replying to an email that has a long thread, it will be inserted at the bottom of the thread.

- Give us an option to select the already set signatures in each account, if possible.
- Option to insert the signature at the cursor position.

This review is for a previous version of the add-on (2.3.1).