A couple of ideas on this --
1.) Some visuals, although not the table card, have a feature called annotations. Depending on your table structure you could show a data table below a bar chart (or another chart that supports annotations) to leave commentary. Here's an example where I call out 'look at all this cake' when planning a super soft birthday party.
2.) Another idea is, depending on how your table is structured and source you might be able to add a 'commentary column' and show the comments in this way. You could probably also write a beastmode case statement to write a commentary column.
3.) You can add a rich text card to write commentary in that could be paired with a table. Here's an example of where to find that and an example of some notes being written and a screenshot being inserted. These boxes support lists, text, images, tables, links and smart text.
Hope this helps.
Might be a cool idea to request annotations being added to table cards in the idea exchange.
