Bug in Special:LanguageStats
It looks as though some of the groups have been weirdly nested so that when I expand "Extensions used by Wikimedia" I get several groups (amongs these "Extensions used by Wikimedia - Main") twice.
Will look into this at some point, but currently it's not important enough...
I also regularly stumble over the strange, and repetitive, nesting. Not a problem, only somewhat bewildering at times.
If you look into in and if that fits into looking into it by the way: We have some checks for correct inputs such as are all $n-s used? that are switched on or off for individual messages at times but are kept in a global file for all messages of all groups. Should they not be collected on a per-group or per-product basis, in the respective repsitories? That would allow to shift responsibility for keeping them up to date towards the product maintainers where that is desirable.
Created a phabricator ticket (with priority:Low) since that is (in retrospect) the more appropriate location. Closing this.