playful → created an issue. See original summary → .
@maria.dis, there's a contrib module for that called autocomplete_id.
This issue persists as a fairly significant UX issue. Drupal needs to be able to work well for users that are neither site nor content administrators. For them, the appearance of the entity ID in autoselect forms is completely extraneous in most cases. The contrib modules chosen and select2 do resolve the issue for select lists. The problem with using a select list widget instead of autocomplete is that the placeholder text for an optional field is "- None -" which is also not easily customizable--a separate UX issue for select lists. But this thread is about the autocomplete widget, and there is still not a solution. Displaying website codes that add visual noise and can confuse front end users should at most be optional, and definitely not required by default. I suggest changing the issue to a bug report.