Base 256: that's an implementation detail.
Little-endian: that's an implementation detail.
My Smalltalk uses base 65536 native-endian and
takes some care not to let Smalltalk code find out.
(Not least because on 64-bit machines I want to
use base 2**32.)
For *private* methods, depending on otherwise
hidden implementation details is fair enough.
My Smalltalk picked up a convention from Squeak
-- or rather, from the Squeak mailing list --
that a 'pvt' prefix on a selector makes it truly
private and *enforces* that.�� Pharo does not seem
to have anything similar, and #at: is the epitome
of a selector in extremely wide general use.
Since #digitAt: exists -- and is what the integer
classes use -- it is practically certain that #at:
is sent to an integer only by mistake.