Change 344062 had a related patch set uploaded (by JGirault):
[wikimedia/portals] Prevents the callback from being called twice

https://gerrit.wikimedia.org/r/344062

@debt For clarification, the compatibility guidelines are stating “MediaWiki may serve these browsers a JavaScript-less environment”. In real-world it comes down to not serving JS to these browsers at all any more and go with a non-JS environment to basically enable users to read the page and fundamentally interact with it. Just last week it was announced that Internet Explorer 9 will be JavaScript-less from April 2017 on. Serving to and testing JS functionality in Opera 11.x is an unnecessary burden for devs and not worth the time investment.

Change 344062 merged by jenkins-bot:
[wikimedia/portals@master] Prevents the callback from being called twice

https://gerrit.wikimedia.org/r/344062

Thanks for the clarification, @Volker_E, and I completely agree that this fix is very low priority and that browsers that old should be shown the JS-less version of the portal.

Old Operas are used by some orthodox Opera fans who want to use it as it was before it became just another Chromium browser. I think at least latest version on its own engine should still be supported for some years

@Base: General browser compatibility wishes could be discussed on the talk page of https://www.mediawiki.org/wiki/Compatibility#Browser_support_matrix please

I am not the one who started :P