Hi Pik ,
You can create a custom control that inherits from Telerik.Sitefinity.Web.UI.PublicControls.LoginControl. The control has public properties that you can override
public virtual string UserName
public virtual string Password
so you can set ToLower.
You need to override the CreateUserForm as well so that you will have unified names/password.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items