I would maintain that your program has more string manipulation for error messages and logging than for generating localised formatted names.

Further I do say that if you're creating text for presenting to the user then the most common operation would be replacement of some field in pre-defined text.

In your case I would design it so that the correctly capitalised first name, surname, and variations of those for sorting would be generated at the data entry point (manually or automatically) and then just used when needed in user facing text generation. Therefore the only string operation needed would be replacement of placeholders like the fmt and standard library provide. This uses more memory and storage but these are cheaper now.