At Fantasy Postseason, we do not natively support playoff survivor pools.  That is, if a commish wants to eliminate fantasy teams, they will need to determine which teams to eliminate and then eliminate those fantasy teams manually.  There are a few ways to accomplish this:

(1) Remove Eliminated Teams From League

The commissioner can remove fantasy teams from the league via the 'Owner Management' page (accessed via the 'Admin' tab on the league home page).  Removed teams will no longer be able to access the league.

(2) Prevent Teams from Accumulating Further Scores

The commissioner can drop the entire roster of a fantasy team via the 'Roster Management' page (on the 'Admin' tab).  Empty rosters will not score additional fantasy points.  Note that in a league that allows free agency (or additional player pick ups) the commissioner will need to take additional action to prevent eliminated managers from adding players back. The commissioner can Freeze an eliminated team via the 'Owner Management' page to prevent any further free agent pickups. One side effect though of freezing a team is that they will no longer be able to post to the league's message board. 

(3) Add an 'Anchor' Score To Eliminated Teams

The commissioner can add a large negative scoring adjustment (such as -1000) to teams that have been eliminated via the 'Per Player Scoring Adjustment' tool (on the 'Admin' tab). This is admittedly a hack, but this action would effectively remove any of these teams from contention.

 

Addendum: Resetting Scores After A Round

If a league has a policy to clear out the scores after a round, thereby forcing all surviving teams to start the next round with 0 points, the best way to do this is to use the 'Modify League Settings' page and update the 'Per Round Scoring Multipliers' accordingly.  For example, after round 1, the multiplier for Round 1 should be set to 0.