The new death messages do not conform to the norms for internationalization. They assume you can break down sentences into parts that will be recombined using something like English grammar. This is not so.
death.cause.kill: %1$s %2$s
death.cause.assist: %1$s %2$s and %3$s
death.fell.by.accident: fell %1$s
death.fell.by.killer: was %1$s
death.fell.by.assist: was %1$s by %2$s
death.fell.cause.arrow: shot %1$s
These and many more assume a particular word order making them untranslatable in many languages.
In Irish (& all Celtic languages) word order is Verb Subject Object. You can't just use fragments starting with "was" because the verb has to come before the subject! The same goes for a fragment like "died". What am I supposed to do with that? You are assuming that the verb comes second when in Irish it's complex expression - Fuair X bás "X died".
Assumptions in programming are bad. Same goes for internationalization.
It would be nice to see Mojang take translations a little more seriously.