Hi Carlos, I'm not sure if this was supposed to be a response to Maria's question about getting "nice names" from the GeoChart. If so, I interpreted the question as her wanting to query the GeoChart for the official name of an area (such as the imaginary api GeoChart.getOfficialName('RU') -> 'Russia'), not as her wanting to show names directly on the GeoChart. If I misinterpreted her question, I apologize, and displayMode: 'text' is indeed a decent solution.
If it wasn't a response to Maria's question, and simply a comment on how displayMode: 'text' is undocumented, then thank you for making us aware of this. We are constantly working hard to improve our code and documentation, but sometimes things slip through. We are now more aware of this than we were, and the documentation will hopefully come soon (though as a primer, it's very similar to 'markers' mode, and all the options should apply to it in the same way that they apply to markers).