Rated 4 out of 5 stars

what is it with addons regularly becoming incompatible with thunderbird? the extension works fine when it does, but messes up the filters when it is incompatible. would give full 5* if did not invalidate filters when incompatible. maybe set them to inactive somehow?
Edit: in case it is unclear, i do not blame the developer for extensions becomming incompatible, on the contrary i appreciate the effort put in so far and realize they are not to blame. furthermore, i hope that average-Joe users (me) complaint is forwarded to the core TB devs, as it seems they lost touch with the base.

This review is for a previous version of the add-on (2.0). 

This comes from Mozilla's constant changes. They have a big one in preparation the switch to "mail extensions" which is what Firefox did a few years back when _they_ pulled the plug on legacy Add-ons. Thunderbird uses the Firefox code base (mozilla-central) as foundation, so they had to eventually follow suit.

This means Add-ons are only allowed special restricted APIs for carrying out their tasks - these are not complete!

Since we are not there yet (I would say not even 5% of what sophisticated Add-ons need in the Mail sphere) there is an interim step - packaging the Add-on as a "mail experiment". but this takes time and resources (and will still break functionality if not done correctly) - we have spent 250hours on conversion efforst for my Add-ons, but the paid licensed ones will have to be completed first before I can do it with the "free as in beer" ones. It is very hard to find developers with this knowledge!

If you are or know a developer who would like to get involved please feel free to leave a comment here:
https://github.com/RealRaven2000/FiltaQuilla/issues/64

If you want to help fund raising for converting FiltaQuilla consider buying a license for quickFilters Pro.