VSTO comment RCW points to the wrong comment

Question

I've come across a very strange behavior in Word VSTO. I don't know why it is happening or how to avoid it. I can demonstrate it with the following code. If _comment is set, then show its content in a MessageBox. If _comment is not set, then set it to the first comment in the document.

    private void Application_DocumentBeforeSave(Word.Document Doc, ref bool SaveAsUI, ref bool Cancel)
    {
        if(_comment != null)
        {
            MessageBox.Show(_comment.Range.Text);
        }
        else
        {
            var comments = Application.ActiveDocument.Range().Comments;
            if (comments.Count > 0)
            {
                _comment = comments[1];
            }
        }
    }

The strange behavior happens when the user adds a second comment with the exact same scope as the first. When that happens, _comment refers to the second comment instead of the first.

_comment is set to some comment:

The user adds a second comment with the same scope as the first (when nothing is highlighted, the word the cursor is in will be selected)

_comment now refers to the second comment, for some reason:

Can anyone explain what is happening here? Am I missing something, or is this a bug in the interop?