> you should make a case by example

Did you read comments of this issue and my email thread on python-dev? There are differents examples:

 - LONG_MAX is 9223372036854775807 even on 32 bits system
 - On Mac OS X, FAT programs contains 32 and 64 binaries, whereas constants are changed for 32 or 64 bits

> we cannot simply drop the modules. Some of the constants
> are needed for e.g. socket, ctypes or ldd programming.

Ah? I removed all plat-* directories and ran the full test suite: no failure. The Python socket modules contain many constants (SOCK_*, AF_*,  SO_*, ...):
http://docs.python.org/library/socket.html#socket.AF_UNIX

Which constants are used by the ctypes modules or can be used by modules using ctypes? Can you give examples? I listed usages of plat-* modules in the first message of my thread on python-dev.

By "ldd", you mean "ld.so" (dlopen)? Yes, I agree that we need to expose  dl constants. But the other constants are not used.