The refactoring I’m talking about is recommended by resharper when it sees a lambda that consists entirely of a method call that is passed the object that is the parameter to the lambda. Here is an example:

public class IWishIWasAScriptingLanguage
{
  public void SoIWouldntNeedAllThisJunk()
  {
      (new List<int> {1, 2, 3, 4}).Select(n => IsEven(n));
  }

  private bool IsEven(int number)
  {
      return number%2 == 0;
  }
}

When resharper gets to n => IsEven(n) it underlines the lambda with a green squiggly telling me that the code can be replaced with a method group. If I apply the refactoring the code becomes:

public class IWishIWasAScriptingLanguage
{
  public void SoIWouldntNeedAllThisJunk()
  {
      (new List<int> {1, 2, 3, 4}).Select(IsEven);
  }

  private bool IsEven(int number)
  {
      return number%2 == 0;
  }
}

The method group syntax implies that the lambda’s parameter is the same as the IsEven method’s parameter. So a readable, explicit syntax has been replaced with an obfuscated, implicit syntax. That is why the method group refactoring is evil.