LibreOffice 26.8 adds basic support for importing and exporting a range of chart types that Microsoft Office includes in OOXML files: box-and-whisker, funnel, Pareto, radial, treemap and waterfall charts. LibreOffice is unable to display or edit these charts, but it does recognise them, informs the user that the chart type is not yet supported, preserves the underlying definition unchanged, and rewrites it when the file is saved. At first glance, this appears to be an admission of incompleteness, whereas it is actually an example of what implementing a proprietary format entails when the aim is interoperability – for the benefit of users, rather than a commercial strategy that treats users as mere tools. What happened Microsoft added these chart types to Office from 2016 onwards, storing them in a namespace generally referred to as ‘chartex’. The namespace is not part of the ISO/IEC 29500 text approved as an international standard, but is documented separately in Microsoft’s extension documentation. This is entirely legal and perfectly normal commercial behaviour: a vendor improves its product and the file format evolves accordingly. The consequence, however, is that the format in everyday use is no longer the one that was standardised. The ISO number continues