I had a server member of replSet asyaRS.

I restarted the mongod with --replSet NotAsya and it happily came up and identified itself as member of asyaRS (since local already had the repl set config there).

It would be safer if we instead complained about replSet argument on command line not matching the stored one.

> rs.conf()._id
asyaRS
> rs.status().set
asyaRS
> db.serverCmdLineOpts().parsed.replication
{ "replSet" : "NotAsya" }