I was trying to use the URL
https://en.wikipedia.org/wiki/Special:MyPage/common.js?action=edit&debug=1
when reporting another bug, but I noticed that the "&debug=1" is discarded after the page redirects to my real page. This also happens with other parameters as well:
https://en.wikipedia.org/wiki/Special:MyPage/common.js?uselang=ja&action=edit&debug=1
It seems that only the "action" is always kept.
Version: 1.19
Severity: enhancement