There is an ongoing sorting problem in Holland Dutch. May be in other languages too. See MDL-58703
In short: sorting on the last part of a lastname, omitting the prefix of that last name. A related problem occurs with third party software (like a SIS) having separate fields for the prefix and the main part of the last name.
Please comment on the bug if that seems to be a problem in your language too and how you solved it (or want it to be solved)