[Svip]

Well, even the Hovercards under Beta features also require a user account. And of course, there is the downside of now only having it enabled on the English Wikipedia.

What about the German or French Wikipedia? What about Wiktionary? Oh man, that is going to be hard.

Indeed, Navigation popups is not perfect and it is intended for editors first. But I mostly use it for speeding up my browsing.

But writing a general tool for all MediaWiki installations is going to be quite the task; a lot of MediaWiki wikis don't even have opening paragraphs like Wikipedia does (see Wiktionary for example). Sure, we can make some compromises and accept that non-encyclopaedia styled wikis don't apply to this tool.

I'd love to see a Firefox extension that did this. But for now; either Hovercards or Navigation popups provides the basics of the requested functionality.