While the new multiline sprintf %O looks snazzy, it will break code for everyone that uses it to ensure that a string contains no "bad" characters. Think log files, one line per entry. This needs to be reverted IMO as the effects on applications are hard to determine.
For reference: Pike v7.7 release 23 running Hilfe v3.5 (Incremental Pike Frontend)
"foo\nbar";
(1) Result: "foo\n" "bar"