1movedto2 ("moved [[$1]] to [[$2]]") and 1movedto2_redir ("moved [[$1]] to [[$2]] over redirect") were translated a long time ago and exported to cyWP. However, the default translations from translatewiki.net have disappeared from cyWP. Is this because they have been replaced by other messages? If so, why are they still in the list of messages? My original Welsh messages on cyWP dating from the time before translatewiki.net existed were deleted in 2008, because they were identical to the default message from translatewiki.net. I have resurrected the messages on cyWP now because I am not sure what is going on, and whether they are still needed for old log entries.
I just wanted to say that those messages are still appearing among the Special:AllMessages list on Wikipedias. Though, I think they are unused messages.
Those messages are only used to support the UDP/IRC feed output until better recent changes feed replacement has been implemented.
I still don't understand why the default messages from translatewiki.net, which were localised and exported to cyWP ages ago, have now disappeared from the cy messages file in MediaWiki (the default message in cyWP is now in English again). This appears to have happened to all languages, not just cy.