Review for Signature Switch by DonCoryon
Not yet rated
This add-on, while well intentioned, falls drastically short of what it tries to accomplish.
Features it doesn't have:
*** Ability to place signature under your reply. (it puts your signature at the bottom of the email regardless of how many replies are beneath, thus making a signature pointless)
*** It also forces you to make a text file, save it somewhere, then point to it.
Use the extension Quick Text:
https://addons.mozilla.org/en-US/thunderbird/addon/640
Works just like Outlook's signature feature.
To create your own collections, you must have a Mozilla Add-ons account.