This attribute is needed to keep certain parts of the text together (e.g. keep text + its superscript or subscript together, keep a word that uses different styles together). Below are examples of such text, where the superscript / subscript words need to be kept together with the "parent" text, and "Uncopyrightable" is a word without spaces, but where part of the word uses a different style. To keep these parts together, they could be wrapped in a <span style="white-space: nowrap;"> tag.

P.S. It seems more logical to me to implement text wrapping using spaces rather than spaces + tags used, as it is now. But the support team have assured me that this is not possible.