{{#babel:en}} does not add a page to the User-pl category on plwikisource (Mediawiki 1.20wmf9).
It works OK on plwiki (Mediawiki 1.20wmf8) and frwikisource (also Mediawiki 1.20wmf9)
Babel 1.7.4 everywhere.
Version: unspecified
Severity: normal
URL: https://pl.wikisource.org/wiki/Wiki%C5%BAr%C3%B3d%C5%82a:Skryptorium/Pulpit_techniczny#Nazewnictwo_kategorii_j.C4.99zykowych_dla_u.C5.BCytkownik.C3.B3w