Docs: "Why do deleted keys show up during range scans?"

[AJ]

http://wiki.apache.org/cassandra/FAQ#range_ghosts
"So to special case leaving out result entries for deletions, we would 
have to check the entire rest of the row to make sure there is no 
undeleted data anywhere else either (in which case leaving the key out 
would be an error)."

The above doesn't read well and I don't get it.  Can anyone rephrase it 
or elaborate?

Thanks!