LCS has a number of minor issues (maybe major depending on your perspective).
LCS is primarily used for wide rows so for instance when you repair data in LCS you end up with a copy of an entire repaired row in L0. Over time if you repair you end up with multiple copies of a row in L0 - L5. This can make predicting disk usage confusing.
Another issue is cleaning up tombstoned data. If a tombstone lives in level 1 and data for the cell lives in level 5 the data will not be reclaimed from disk until the tombstone reaches level 5.
I propose we add a "major" compaction for LCS that forces consolidation of data to level 5 to address these.