Am 03.07.2012 um 18:19 schrieb luigi scarso:

(\vcenter is a TeX primitive)

ConTeXt redefines \vcenter because the primitive can only be used in math mode.
yes I know ... and  original TeX primitive is still available as \normalvcenter
(kind of easter egg for Alan..)

All primitives are available as \normal… and sometimes it’s the only way to use
them because the names are used for other commands, e.g. \unexpanded.

Wolfgang