I've had a quick look through the demo admin and cannot find where things such as settings for whether/not comments require moderation, login and so on.
Are settings such as these accessible through the admin interface and if so, where?
If not then are they settable via an external configuration file, or direct editing of a database table?
The same would apply to a forum and whether to require moderation and/or login of messages posted...
There seems to be an absence of access to 'administrative' type settings in the admin interface... That's in keeping with it being more content oriented, and settings typically are made once and then left alone. But how is it done in SilverStripe?
There seems to be an absence of access to 'administrative' type settings in the admin interface
Yes, this is one of the design features of the SilverStripe CMS. Allow the developers control of the settings via the _config.php file and let the content authors deal with the content. A few page by page settings are defined in the CMS (eg basic access rights for the page, turning comments on/off) but for the large part the idea is to keep most of the developer features in the code.