It seems Notepad++'s "search + replace all" feature replaces text in place inside a search context rather than buffering the changes and applying them outside a

It seems Notepad++'s "search + replace all" feature replaces text in place inside a search context rather than buffering the changes and applying them outside a search context after the search is complete. This makes search recursive. When combined with enhanced regexes (backreferences and lookahead), you have the ingredients for Turing completeness.