HTML5-mode was briefly switched on for Wikimedia wikis this week, from the afternoon of February 23. This would begin the process of Wikimedia supporting features available in the newest browsers, and would generally put it on a better footing for the future. HTML5 had been the default for external installs since MediaWiki 1.16, but had been disabled on WMF sites due to the nature of some custom code in use. Version 1.17, now used on WMF sites, was thought to be much more stable in this regard (bug #27478).
However, after deployment, a number of errors were soon noted. As expected, virtually every tool which relied on "screen-scraping" (analysing the HTML source of Wikipedia pages) broke in some way. Though this method has been known to be vulnerable to changes in the underlying source code for many years – and MediaWiki provides an alternative, the much more stable API, for this purpose – no-one had yet seen a need to update many of the tools frequently in use on Wikipedia sites, including Twinkle and Friendly on the English Wikipedia. Even after HTML5-mode was reverted, work continued on these gadgets to move them over to the API before another attempted deployment. Just as pressing was a knock-on problem where the encoding used in citations and anchors changed subtly, breaking links which relied on them (bug #27694). It is not known when HTML5-mode will be tried again.
Not all fixes may have gone live to WMF sites at the time of writing; some may not be scheduled to go live for many weeks.
As of the time of writing, file description pages for images on Wikimedia Commons are no longer being transcluded into local file namespaces. The cause remains unknown (bug #27767). Update: this bug has been resolved.
With the WMF install of MediaWiki 1.17 complete, developers have been "sprinting" to get it ready for release to other sites. The main point of contention has been the new installer (wikitech-l mailing list).
The upload of 1.8 million images from the United Kingdom-based Geograph project has resumed after technical difficulties brought complaints (Gerard Meijssen).
XML dumps have been restarted after the 1.17 deployment. Reusers should be aware that their form has been updated slightly (wikitech-l mailing list).
Shiju Alex and Gerard Meijssen  blogged about a new MediaWiki extension called "Narayam", which provides input methods for Hindi, Malayalam, Tamil, Kannada, Marathi, Bhojpuri, Sanskrit, and Bengali, making contributions in those languages much easier.