Rated 5 out of 5 stars

The idea here is 5-star: A good black theme. Much appreciation for the work, but it messes with the fonts way too much. Perhaps a different version is needed that simply changes the colors and leaves the fonts (including line spacing) alone. Deleted three lines in root.css to get default fonts back, but no time now to restore line spacing, will mess with later. If color-only pkg is released, please post!

Changing to 5-stars. Found line spacings dependent on variables also set in root.css, knocked down to 20px default, and everything looks great. For any who want to do the same, the two lines are:
--message-list-row-height: 20px;
--folder-tree-row-height : 20px;

Many thanks for a great extension!

This review is for a previous version of the add-on (2.1). 

Hi FFnut, now you can change the heights direcly from the addon settings. For the other issues, please open an issue on GitHub: