This seems like a natural candidate for automated browser testing, but there are a lot of combinations. I don't know of any platform currently available at WMF that would let us test experimental code on *every* wiki.
We can affect:
- Page save (job is enqueued, so this is usually safe to end-users).
We're currently deployed to wikis listed in $wmgUseORES.
We plan to extend support to these wikis: