Per T153334, the consensus seems to be that the best way forward is to implement Unicode section IDs and percent-encoded fragments in MediaWiki URLs. For backwards-compatibility with existing saved URLs, we would add empty span tags with the old dot-encoded section IDs.
We already know that this implementation works with all current browsers, but we need to see how far back the support goes. Test percent-encoded fragments and Unicode section IDs (i.e. anchors) on all [[ https://www.browserstack.com/ | available browser versions ]] until it is determined which version of each is the oldest to support this implementation. This should allow you to answer the following questions:
* What is the oldest version of Firefox to support this implementation?
* Safari?
* Chrome?
* Internet Explorer?
* Mobile Safari?
* Chrome Mobile?
* Android Web Browser?
* Do all [[ https://www.mediawiki.org/wiki/Compatibility#Browser_support_matrix | "modern browsers" ]] support this implementation?
Here is a test page: https://kaldari.github.io/scratchpad/unicode-fragment.html. Browser support should be considered passing if all 3 test cases pass.