What solutions exist for including free format rich text data within an Excel file

What solutions exist (and what are the pros/cons) for including free-format, rich text data in an Excel file (along side the normal tabular data)?

This is the kind of data I'd like to include (in a separate worksheet):

Note that we're currently using openpyxl to generate Excel files from Python. We can use something other than Python/OpenPyXL if necessary, but keeping with Excel is a must (the accountants who use these reports won't use anything else).

The Excel specification makes it pretty tricky to do what you want. Currently, the smallest unit that you can apply styles to in openpyxl is a cell. As long as you can work with that restriction, you should be okay. Outlining is also supported.