Replication related events in logfiles can only be interpreted in the context of the replica set configuration at the time the line was logged.

We log that reconfig events have occurred, both when we get a replSetReconfig command, and getting a new config from a remote, but not the actual configuration (either the previous or the new one).

Logging the full contents of the before/after config documents whenever it changes would greatly assist with the correct interpretation of subsequent replSet events that occur in the logfile, particularly when there is limited/missing external information about the reconfigs that have occurred.