EDIT after developer's input: worth another star. The app does have visual feedback of the success of adding the torrent, it was my FF installation. Highly recommended, impeccable extension and developer !
The only missing piece I think is a better feedback. Right now, we do have sound feedback for the torrent adding, but it's not really useful when working with computers with no sound or intentionally muted. Plus the sound is a beep, that can seem like an "error sound" instead of a "success sound". An unintrusive popup or toast informing the user that everything went smoothly is a must, otherwise we're left wondering if it worked at all. I've seen similar plugins that show a small text bubble close to the link you just clicked that triggered the torrent adding.Another thing, the source code on http://www.alexisbrunet.com/ seems outdated, not corresponding to the latest version available on https://addons.mozilla.org
The addon already has a popup message that appears in the bottom right hand corner of the screen whenever you click a torrent link that will show you success or failure messages. If the popup message is not working for you please let me know.
The original source code from alexis brunet has not been updated for several years. This addon is one I've been updating and maintaining since he stopped working on his.