Please note that some updates of English strings are pretty important. As an illustrative example, take the string [renameto,core_repository] that was updated in 2.3 in the following way. In Moodle 2.2, it reads
Rename to
while in Moodle 2.3 it is defined as
Rename to "{$a}"
If you don't update your translation in 2.3 to contain the new placeholder, there is an information-loss expected in the user interface.