Apparently Echo pings are not recognized if the signature uses custom namespace alias (defined per-wiki, rather than for the language).
Support for localised namespaces was implemented per bug 53132, but custom aliases don't work.
Version: master
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=53132
https://bugzilla.wikimedia.org/show_bug.cgi?id=73366