Users sometimes use a different link label in their signature. E.g. [[User:Jdforrester|James F.]]. It is also used when users want to transliterate their name into a different script, e.g. [[User:קיפודנחש| קיפודנחש (aka kipod)]] (https://en.wikipedia.org/wiki/Talk:Hewlett-Packard_9100A?dtenable=1)
As the link label is the only thing that is shown on the page, this should be included in the list of autocomplete suggestions.