It is not possible to change the configuration for Discussions/Viewing.
Steps to recreate:
1. Select 'Help&Account' from http://slashdot.org
2. Select "Discussions - Viewing"
(The discussion viewing configuration user interface is shown).
3. Change some options, for example, change Retrieve from "few" to "many"
4. Press "Save"
5. Go back into "Discussions - Viewing"
Note that the options that were changed and 'saved' have reverted back to their original values.
Effectively it is no longer possible to configure discussion viewing.
Browser used: Firefox 3.6.7 on CentOS 5