Currently if a config server inconsistency is detected, we only disallow starting new mongoS'es, autosplits and the balancer. However, sharding new collections/databases is allowed, as well as manual chunk splits and moves.

Ongoing manual metadata operations are often triggered by scripts, so if they are not failing it's not possible to detect the erroneous condition.

Further, it's not possible to predict the full scope consequences of metadata alterations when config servers are not consistent.