edits: clarifications to wording in the write concern section

Author: Sam Kleinman

source/applications/replication.txt

@@ -22,11 +22,12 @@ Write Concern
 When a :term:`client` sends a write operation to a database server,
 the operation will return without waiting for the operation to succeed
 or return. To verify that the operation is successful, use the
-:dbcommand:`getLastError` command. :dbcommand:`getLastError` is
-configurable and can wait to return for journal writes or full disk
-flush. For replica sets, :dbcommand:`getLastError` can return only
-when the write operation has propagated to more than one node, or a
-majority of nodes in the set.
+:dbcommand:`getLastError` command. You can configure
+:dbcommand:`getLastError` to return after journal flushes to disk or
+after the data itself flushes to disk. For replica sets, you can
+configure :dbcommand:`getLastError` to return only after the write
+operation has propagated to more than one member of the set or to a
+majority of the set's members.
 
 Many drivers have a "safe" or "write concern" mode that automatically
 issues a :dbcommand:`getLastError` command following write