but the file appears to be progamming language
It's JSON. It's just Javascript object code to store the data (as opposed to doing it with an ini file, XML file or HTML file for example).
https://en.wikipedia.org/wiki/JSON
http://www.json.org/
Just thought there would be an easier way to list the speeddial sites.
As suggested, after wiping out Opera's profile (which you're doing be reinstalling the OS) and reinstalling Opera, you'd just replace the current Bookmarks file with your old one.
However, doing it the way you're doing by just keeping the list in a text file and adding the speeddials manually again will ensure that the new Bookmarks file isn't messed up or hijacked in any way. If you still have the old file though, you can look through it to see if there are any URLs to some of the sites you were being redirected to.
As others have said, even though it is only happening in Opera, it is still possible (at least) that it is something outside of Opera. But, since you're wiping everything out, that should doesn't matter.