How to format comments in a cell using XlsIO

IRange range = worksheet.Range["A1"];
string commentText = "Hello World";
 
//Adding RichText comment to cell
range.AddComment().RichText.Text = commentText;
IRichTextString rtf = range.Comment.RichText;
            
//Formatting the comment
IFont font = workbook.CreateFont();
font.Italic = true;
font.Size = 15;
rtf.SetFont(0, commentText.Length, font);

Dim range As IRange = worksheet.Range("A1")
Dim commentText As String = "Hello World"
            
'Adding RichText comment to cell
range.AddComment().RichText.Text = commentText
Dim rtf As IRichTextString = range.Comment.RichText
 
'Formatting the comment
Dim font As IFont = workbook.CreateFont()
font.Italic = True
font.Size = 15
           
 rtf.SetFont(0, commentText.Length, font)