Interface reference counting in Delphi Supports function - delphi

Question

I have class THuman which implements interface ICanTalk.
But whenever I try to check if human can talk, Supports function destroys object instance, despite the reference in the code.
What did I misunderstood?
procedure TForm1.Button1Click(Sender: TObject);
var
Obj:TInterfacedObject;
begin
Obj:=THuman.Create('Great guy');
// if Supports(Obj, ICanTalk) then //Object destroyed here if uncommented
(Obj as ICanTalk).TalkTo(Memo1.Lines);
end;
Implementation
ICanTalk = interface
['{57E5EF90-EB11-421C-AAFB-18CD789C0956}']
procedure TalkTo(List:TStrings);
end;
THuman = class(TInterfacedObject, ICanTalk)
private
FName: string;
public
procedure TalkTo(List:TStrings);
property Name:string read FName;
constructor Create(const AName:string);
end;
constructor THuman.Create(const AName: string);
begin
FName:=AName;
end;
procedure THuman.TalkTo(List: TStrings);
begin
List.Add(Name+' says Hello World!');
end;

Answer 1

This is expected. When you read the documentation about the Supports function, you found this:
Warning
With the exception of the overload that checks whether a TClass implements an interface, all the other versions of Supports will extract an interface reference either from an object or from another interface reference, causing the reference count of the underlying object to be incremented, and then will release the interface upon exit (decrementing the reference count). For objects that have a reference count of zero, this will result in the object destruction.
var
Obj: TInterfacedObject;
begin
Obj := TInterfacedObject.Create;
if Supports(Obj, IInterface) then { ... at this point Obj will be freed }
end;
You wrote,
despite the reference in the code(in visible area)
No, there is no reference. You declared Obj as TInterfacedObject (a class instance variable -- not an interface variable), and so there is no reference counting.
If you instead use an interface-typed variable, it will use reference counting:
var
Obj: IInterface;

Answer 2

This behavior really annoyed me. Why did Embarcadero not declare the internal variable as [unsafe]. In the following example, the object is only released with FreeAndNil. Alternatively, you can use TInterfacedPersistent instead of TInterfacedObject. Then you always have to release the object yourself.
program Project3;
{$APPTYPE CONSOLE}
{$R *.res}
uses
System.SysUtils;
type
ICanTalk = interface
['{57E5EF90-EB11-421C-AAFB-18CD789C0956}']
procedure TalkTo;
end;
THuman = class(TInterfacedObject, ICanTalk)
public
destructor Destroy; override;
private
FName: string;
public
procedure TalkTo;
end;
procedure THuman.TalkTo;
begin
end;
destructor THuman.Destroy;
begin
inherited;
end;
var
o : THuman;
[unsafe]
intf : IInterface;
begin
try
o := THuman.Create;
Supports(o, ICanTalk, intf);
Intf := nil; //Didn't call destructor cause of [unsafe]!
FreeAndNil(o); //Call destructor!
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end.