var wb = new XLWorkbook();
var ws = wb.Worksheets.Add("Margins");
ws.Cell("A2").Comment
.SetVisible()
.AddText("Lorem ipsum dolor sit amet, adipiscing elit. ").AddNewLine()
.AddText("Nunc elementum, sapien a ultrices, commodo nisl. ").AddNewLine()
.AddText("Consequat erat lectus a nisi. Aliquam facilisis.");
ws.Cell("A2").Comment.Style
.Margins.SetAll(0.25)
.Size.SetAutomaticSize();
wb.SaveAs("CommentsMargins.xlsx");