When performing a compaction on two sstables that contain the same RangeTombstone with different timestamps, the tombstones are not merged in the new sstable.
This has been tested using cassandra 2.1 with the following table:
And then doing the following:
When checking with the SSTableExport tool two tombstones exists in the compacted sstable. This can be repeated, resulting in more and more tombstones.