It's very easy to reproduce. Just perform a few deletes and you will see that compaction is not purging the tombstones at all if the only_purge_repaired_tombstones option is set. There is a bug in the patch for
CASSANDRA-6434. The corresponding unit test (RepairedDataTombstonesTest) is also weak in that it does not catch the bug. Attached is a patch which fixes the bug and the unit test.