There are several reasons for a method not to have a method body:

It is an unintentional omission, and should be fixed to prevent an unexpected behavior in production.
It is not yet, or never will be, supported. In this case remove it.
The method is an intentionally-blank override. In this case a nested comment should explain the reason for the blank override.

Noncompliant Code Example

ClassMethod foo() As %String
{
}

ClassMethod bar() As %String
{
}

Compliant Solution

ClassMethod foo() As %String
{
    Quit "Hello"
}

ClassMethod bar() As %String
{
    // We need to do something here
}