It works! The downside is that any double click (enlarging a map or highlighting a link) also closes the tab. If the sensitivity or the timing of the clicks could be adjusted it would be a really helpful extension. Sadly I had to disable it. Way too many tabs disappeared.
Can you please open an issue at https://github.com/Smile4ever/firefoxaddons/issues/ where you state some problems including your ideas how to solve them?
In the mean time, can you try out https://cup.aihedy.com/firefox/addon/middle-click-on-page-close-tab/ ?
