Rated 4 out of 5 stars

Very good application. However, I would like to know if that would be possible having the orthographic correction suggestions that corresponds to the thunderbird settings. I have chosen French for my Thunderbird, but the language is not recognized in the Whatsapp module and the proposed corrections are only in english.

This review is for a previous version of the add-on (1.3.1). 

Thanks for the good rating and comment :-) For your question, I am not aware of a way to integrate the Thunderbird spell checker into any website. That's also true for Telegram Web in Thunderbird, GCalTab, and for any website browsed with Open Tab. As an alternative, I use LanguageTool and it rocks ;-)