The first time you create Windows Failover Cluster, the node name is added according to DNS name.

If you have set a mix of upper and lower case for node name, the node lists look ugly.

Steps

1. Evict the node with incorrect format

1. Open Command Prompt in Administrator Mode

Windows Server 2008 R2

Cluster.exe /CLUSTER:<CLUSTER_NAME> /ADD /NODE:<CLUSTER_NODE_NAME>

Example:
C:\>Cluster.exe /CLUSTER:HQVHV02C1 /ADD /NODE:HQVHV02C1N2
Configuring node HQVHV02C1N2
---------------------------------------
 12% Validating cluster state on node HQVHV02C1N2.
 25% Getting current node membership of cluster HQVHV02C1.
 37% Adding node HQVHV02C1N2 to Cluster configuration data.
 50% Validating installation of the Microsoft Failover Cluster Virtual Adapter on node HQVHV02C1N2.
 62% Validating installation of the Cluster Disk Driver on node HQVHV02C1N2.
 75% Configuring Cluster Service on node HQVHV02C1N2.
 87% Starting Cluster Service on node HQVHV02C1N2.
 100% Waiting for notification that node HQVHV02C1N2 is a fully functional member of the cluster.

Notes

In future, Microsoft prefers doing this using Powershell.
However, in my test, the node added using Powershell will be in lower case.

Command:
Get-Cluster <CLUSTER_NAME> | Add-ClusterNode <CLUSTER_NODE_NAME>

Example:
Get-Cluster HQVHV02C1 | Add-ClusterNode HQVHV02C1N2