Can people see your level on a language and its reverse tree at same time?
E.g. I'm level 23 on German for English, and just started at level 1 on English for German. Is it possible to see that I have levels in both, or does my German level not show up, now that I've set my native language to German?
Try the page I mentioned. It shows multiple language flags from multiple reverse trees: https://www.duolingo.com/comment/24977590$comment_id=24981012
The streak list on http://www.duolingo.eu does not only list the languages - like SHOF does it - but the page rather shows each course flag you are learning on, including ALL reverse trees (multiple flags of the same language).
I believe the script author (not me) scans the user extended profile details to display that great course summary.