I have done some edits on dewiki and than search for a word of the edit summary and found a user page with contains:
{{Special:Recentchanges/100}}
The snippet was the expanded special page:
(-32) . . Umherirrender (Diskussion | Beiträge) (Standard-ID nutzen - editnotice-ns-3 -> mw-editnotice-3)
It seems useless to add transcluded special pages to the search index, because such pages will expiry very fast.