Recent changes messages
There is no problem. Don't worry about it.
How come? If you have a clean MediaWiki install with a non-English content language, the RC page is going to start with a duplicated message (one from Recentchanges-summary (in your UI language), the other from Recentchangestext (always in content language, this one should not be there)). See e.g. wikiquote:be:Special:RecentChanges.
Can you show me such an out of the box installation?
Really, don't worry about it.
E? I don’t get it. Belarussian Wikiquote is an example of a real working MediaWiki installation suffering from this bug.
I don’t have to worry about this since I have fixed the Czech translation. I just thought somebody might care about the other languages. But OK, I’ll take that as someone else’s problem.
Then it's not a localisation issue, but a code issue. The code I saw meant to prevent this.
The code checks whether the message is - or empty. However we have old translation of this message which are not empty: http://translatewiki.net/w/i.php?title=Special:Translations&message=MediaWiki:Recentchangestext