When a cell value contains commas or new lines, they are not escaped on export to CSV and single value is exported as multiple values.

Workaround: Escape the value manually. For example, use the following extension method to set string cell values:
internal static class CellExporterExtensions
{
    public static void SetValue(this ICellExporter cell, string value, SpreadDocumentFormat format)
    {
        if (format == SpreadDocumentFormat.Csv)
        {
            if (value.Contains(","))
            {
                // escape all quotes with double quotes
                value = value.Replace("\"", "\"\"");

            }

            // enclose all values within quotes
            value = string.Format("\"{0}\"", value);
        }

        cell.SetValue(value);
    }
}

Available in LIB version: 2017.1.403

ArgumentException with clarification similar to  "'\u001f', hexadecimal value 0x1F, is an invalid character." is thrown when trying to export document containing characters which are not supported in XML document - such as some control characters like 0x00, 0x1F, 0x1B, etc. Such characters are described in the XML specification here: https://www.w3.org/TR/xml/#charsets.
Although the escaped strings are not supported (see related 181318), the library could prevent the exception and export the document successfully by skipping such characters.
Workaround: remove such characters before the export. Check the following StackOverflow answer for some ideas on code for replacing the characters: http://stackoverflow.com/a/14323524/259206

Exception when color does have a complete value.

When importing a document containing more than one Number Formats (numFmts) with the same format code (formatCode) an exception is thrown: System.InvalidOperationException: 'Same item with different index exists.'

While reading the content, the ReadCellValue method throws NotSupportedException: "The RichText value type is not supported". Although the rich text in the cells is not supported, the library could parse the text content and avoid throwing errors.

When calling SpreadExporter.CreateWorkbookExporter method and referencing Trial assemblies an exception is thrown: System.ArgumentException: 'An item with the same key has already been added.'

This behavior is observed both with the NuGet packages and DLLs.

It is not observed with Trial DLLs version 2020.3.1019

When using the API for measuring the cell content size the results are not correct.

Exception when exporting a conational formatting rule with no formatting 

Rows import stops after reading a formula cell.