Hi folks,
Starting with version 1.24wmf17 (which will be deployed to production wikis starting August 14), MediaWiki will no longer execute JavaScript code on Microsoft Internet Explorer 6 (previously the cutoff was MSIE5). In short, this version of MSIE has several unpatched vulnerabilities and is no longer actively supported. Running JavaScript for this version of the browser carries a significant maintenance burden without commensurate benefit.
JavaScript fixes specific to IE6 have also been removed. Additional IE6 fixes that exist in MediaWiki:Common.js can be safely removed one MediaWiki 1.24wmf17 is deployed on your wiki.
In general, we are considering putting more outdated browsers in the "no JavaScript" category, while simultaneously putting more effort against ensuring that basic site functions can be used without JavaScript. Likely candidates for this include IE7 (released 2006) and Opera 8.* (released 2005).
We believe this will ultimately benefit both groups of users: Users with outdated browsers get a more consistently tested and more secure experience, while users with modern browsers benefit from faster development.
This will be communicated through tech news as well, but please help carry this message into your communities as appropriate.
All best, Erik