This is a great and well designed translation add-on!

However:
- Automatic switching to second language seems to be not working when selecting text. (reported bug)
- Switching language in the popup box (after clicking the icon) would be good to remember at least till the end of browser session (or another change).
- Using the language (selected in the popup box) as "first" for the context menu action (at least till the end of browser session) would be a great feature.

And again: this is a great and well designed translation add-on!
(I will give 5 stars after fixing the above issues)