User blog comment:BertH/Fluid layout has arrived/@comment-768817-20131205202357/@comment-5052981-20131205230317

Yes it was a beta, so they enabled it on specific wikis.

But lets say if Darwin was optional and 40% of wikis adopted it, then they'd have to maintain Darwin and non-Darwin at the same time.

I personally don't like Darwin, but it makes sense to enable it on all wikis.