Rated 3 out of 5 stars

It works OK but it doesn't support rich text ou HTML. Also, it writes the signature in grey only, preceded with a double dash and we don't have control on those 2 things. Instructions would be much appreciated.

Thank you for your message. random(signature) uses the default signature facilities of Thunderbird. The default behaviour of Thunderbird is to put a double dash above the signature and to display it in grey. I don't know if it even possible to change that and it is also not in the scope of this extension.

For this you may consider using the Signature Switch extension at https://addons.mozilla.org/de/thunderbird/addon/signature-switch/