Why doesn't reference loop detection use reference equality? [closed]

Answer 1

Newtonsoft explicitly addressed this question in Issue #401: Object reference equality should be used when checking for circular references:

I prefer the current behavior which lets devs customize logic by overriding Equals.

Besides, this is a big breaking change.

But then later added:

Added EqualityComparer to JsonSerializer 3cc797c.

This enhancement added support for JsonSerializerSettings.EqualityComparer which allows the default behavior of calling object.Equals in reference loop detection to be overridden in settings:

public IEqualityComparer EqualityComparer { get; set; }

Gets or sets the equality comparer used by the serializer when comparing references.