Why is this an issue?

The use of == to compare two objects is expected to do a reference comparison. That is, it is expected to return true if and only if they are the same object instance. Overloading the operator to do anything else will inevitably lead to the introduction of bugs by callers.

public static bool operator ==(MyType x, MyType y) // Noncompliant: confusing for the caller
{
    // custom implementation
}

On the other hand, overloading it to do exactly that is pointless; that’s what == does by default.

public static bool operator ==(MyType x, MyType y) // Noncompliant: redundant
{
    if (x == null)
    {
        return y == null;
    }

    return object.ReferenceEquals(x,y);
}

Exceptions

• Classes with overloaded operator + or operator - are ignored.
• Classes that implement IComparable<T> or IEquatable<T> most probably behave as value-type objects and are ignored.

Resources

Documentation

• Reference types
• Equality operators