Thread:VisualEditor/Feedback/Why is IE not officially supported?/reply

Internet Explorer is very different (internally) than any other browser, and some of its "features" cause VisualEditor (and most other advanced web tools) to break. It will be officially supported when we think that it's actually working as well as the others. As you noted, things have significantly improved. For a long while, Internet Explorer's "security" system refused to allow editors to save pages. (That's why it was entirely disabled for months: imagine spending a long tim fixing an article, only to have IE refuse to let you save your work at the last second.)