Quicktext "compatible" up to TB 15 Rated 5 out of 5 stars
Here is a modified Quicktext.xpi, configurated to be compatible up to Version 15 of Thunderbird. But its not testet, if quicktext is real compatible with version 10+ of thunderbird!
The new "chrome-like" versioningstrategy of Mozilla FF and TB is absolutly cruel.
XPI-Files ("Addons") are just zipped folders. So you can open/extrat xpi-Files with 7zip.org. Check "install.rdf" inside the xpi and you can see the Compatible-with-Version Configuration.