Why is Scala 2.9.2 version of kafka recommended?

On Kafka download page we saw - "We build for multiple versions of Scala. This only matters if you are using Scala and you want a version built for the same Scala version you use. Otherwise any version should work (2.9.2 is recommended)." Why is Scala 2.9.2 version of kafka recommended?

Purging dead consumer ids from _consumer_offsets?

_consumer_offsets is becoming rather big > 1 TB. Is there a way to purge dead/inactive consumer id rows from it?