Fallback to cs

While it can make a sense to set it in generic MediaWiki installation (although sk as a fallback to cs is quite unusual(*) - I can't recall any software (except for that where sk is the original development language) doing that, everywhere there is a fallback to en or any other worldwide language), it must obtain a consensus on both sides on relevant Wikimedia wikis.

Also mind phabricator:T13267.

(*) besides fallback from language with higher number of speakers to language with lower number of speakers is quite illogical

Wikimedia wikis don't automatically rule MediaWiki i18n; there are hundreds of MediaWiki wikis in Czech and i18n is there to benefit as many users as possible.

There's nothing illogical about a reciprocal fallback, see also the referenced research; the "bigger" language, as defined by number of translation, will simply use the fallback less. Per the list provided above, cs messages falling back to sk are 7 times less than sk to cs. You can probably translate them all in an afternon. :)

Please read properly what I wrote. Both here and in commit message. That would prevent you reacting with useless post.

In a nutshell - by default yes (I don't care), on WMF wikis obtain consensus.

In my opinion the fallback to sk/cs is much better than default fallback to en (e.g. I´m the only one in my large family, who speaks English, but everybody understands Slovak).