Oceniono na 2 z 5 możliwych gwiazdek

The add-on works only with signatures defined in the signature field of your account, which is too bad.
I managed to override the problem by copying the content of my file-sig in the thunderbird-integrated signature field, but that's not a pretty solution IMHO.

Please, add file-sig support, that'd be great.

Ta opinia jest o wcześniejszej wersji dodatku (0.2). 

You can't use a file-signature! If you add your signature into the signature-field it will work...