Rated 2 out of 5 stars

This functionality should be built-in in Thunderbird, but unfortunately it isn't. And unfortunately again, this seems to be the only extension that tried to tackle this, and as others have noted, it leaves a lot to be desired in terms of performance. In fact, the flickering and the general slow-down got so bad that I had to disable it. I hope the developer will fix those obvious issues.

Thanks for your feedback. The flickering is due to Thunderbird high refresh rate and I can't do much about it (or just slow down even more Thunderbird...).
However you can still use the add-on in the message panel by disabling in the settings the display in the inbox list.