Hi Jason,
1) Currently we do not provide support to add "Autoshape" or "Text Box. So, I have created a feature request with the development team
http://www.syncfusion.com/support/features/xlsio/Default.aspx?ToDo=view&questId=1419
I will update you as soon as an estimate is available. Sorry for the inconvenience.
2) Use the following code snippets to insert comments.
[c#]
//Insert Comment.
ICommentShape shapecom = sheet[ "A1" ].AddComment();
//Format Line.
IShapeLineFormat line = sheet.Comments[ 0 ].Line;
shapecom.Text = "hello";
line = shapecom.Line;
line.Weight = 12;
line.ForeColor = Color.Magenta;
line.Style = ExcelShapeLineStyle.Line_Thin_Thick;
Here is the sample for your reference:
comment.zip
3) Could you please provide more details on how Comments are added to chart in MS Excel? This would help me in investigating further on this issue.
Please take a look and let me know if you have any other questions.
Thanks,
Melba