Example:
<sheetViews>
    <sheetView tabSelected="1" view="pageBreakPreview" zoomScaleNormal="100" zoomScaleSheetLayoutView="100" workbookViewId="0">
        <selection activeCell="J5" sqref="J5"/>
    </sheetView>
</sheetViews>

Currently, similar conversions should be manually implemented by the users.

Sample method that could be used:

public static Color HexStringToColor(string hexColor)
{
    // Remove the # at the front.
    if (hexColor.StartsWith("#"))
    {
        hexColor = hexColor.Substring(1, hexColor.Length - 1);
    }

    byte a = 255;
    byte r = 255;
    byte g = 255;
    byte b = 255;

    int start = 0;

    // Handle ARGB strings (8 characters long).
    if (hexColor.Length == 8)
    {
        start = 2;
    }

    //Handle contracted RGB strings (3 characters long)
    if (hexColor.Length == 3)
    {
        hexColor = string.Format("{0}{0}{1}{1}{2}{2}", hexColor[0], hexColor[1], hexColor[2]);
    }
    else if (hexColor.Length < 6)
    {
        hexColor = hexColor.PadLeft(6, '0');
    }

    // Convert RGB characters to bytes.
    r = byte.Parse(hexColor.Substring(start, 2), NumberStyles.HexNumber);
    g = byte.Parse(hexColor.Substring(start + 2, 2), NumberStyles.HexNumber);
    b = byte.Parse(hexColor.Substring(start + 4, 2), NumberStyles.HexNumber);

    return Color.FromArgb(a, r, g, b);
}

Provide ability for working with comments in a spreadsheet document.

In Office 365 there are two types of comments:

1. Comments/Notes
2. Threaded Comments 

This item applies to Threaded Comments only.

For Notes, please follow: SpreadProcessing: Provide API for Insert / Delete Comments (Notes)

With the current implementation, the Notes support only a rectangular shape.

Examples:

SpreadProcessing: Upon export, sheet reference in formulas such as VLOOKUP is lost when using whole row/column references.
For example the formula
=VLOOKUP("test",Sheet1!A:C,1,0) is exported as

=VLOOKUP("test",A:C,1,0)

The values applied to the row/column should be explicitly set on each used cell as well. Otherwise, if they are applied on row/column only, the used cells don't use the desired values when opening the document.

To reproduce:

1. Set some content on cell A1
2. Create a row selection and apply a fill color to it (or any other property)
3. Export the document and open it in an application

Observed: All cells except A1 have the specified color.

Workaround: Use cell selection, e.g.:

sheet.Cells[0,10].SetFill(PatternFill.CreateSolidFill(Colors.Red));

The format applied to the first value of the range of the chart determines the format of the value (vertical) axis. If the format of this value is changed, the model attempts to set a new format to the axis. If the chart does not support axes, the value of its PrimaryAxes property is null, which causes NullReferenceException.