I noticed today that user pages from Meta-Wiki are also indexed from seemingly random wikis, possibly all. e.g. https://sw.wikibooks.org/wiki/Mtumiaji:Krinkle is a result in Google on the second page for my username (not higher than the version from Meta-Wiki, but still).
We should probably mark these as Noindex and/or ensure the Canonical link header is set to the central version?