DOCS-1007 minor correction/clarification

Author: Sam Kleinman

source/administration/sharded-clusters.txt

@@ -326,14 +326,14 @@ different locations within the cluster and have different roles:
   database.
 
 This means that you *can* authenticate to these users and databases
-while connected directly to the primary shard for a database. However,
+while connected directly to the *primary* shard for a database. However,
 for clarity and consistency all interactions between the client and
 the database should use a :program:`mongos` instance.
 
 .. note::
 
    Individual shards can store administrative credentials to their
    instance, which only permit access to a single shard. MongoDB
-   stores these credentials in the shards' :term:`admin databases <admin database>` and these
-   credentials are *completely* distinct from the cluster-wide
-   administrative credentials.
+   stores these credentials in the shards' :term:`admin databases
+   <admin database>` and these credentials are *completely* distinct
+   from the cluster-wide administrative credentials.