Rated 5 out of 5 stars

The issue where dictionaries don't show up in the list is due to changes in how Firefox handles dictionaries and it's not something the author can fix. However, you CAN manually correct the problem: find the location where Firefox stores your dictionaries (C:\Users\[Username]\AppData\Roaming\Mozilla\Firefox\Profiles\[profile_name]\extensions\) then for each dictionary that doesn't show up, find its folder (e.g. "en-gb@...") and edit the install.rdf file. Look for the line "<em:type>64</em:type>" and delete it. Restart Firefox and your dictionaries will be detected properly.

If like me you want to rename the text display which currently uses locale, you can also do so manually. Look for the "dictionaries" subfolder in the folder of the dictionary you want to rename and rename the files you find. For instance, "fr-modern" becomes simply "FR" for me. If a single dictionary has more than one file (most have .dic and .aff), rename both and make sure their names are the same.

I've been in contact with the developer and renaming as well as other display improvements are in fact being developed.

(My original review gave this only four stars due to a graphical glitch. Further investigation revealed that it was caused by a custom theme instead.)

This review is for a previous version of the add-on (1.3.2.1-signed.1-signed).