At the time of my earlier reply, I hadn’t yet done it here and just posted the mod_rewrite rules I use on other web servers. These rules do work.
HOWEVER, having started moving a couple sites over to DH, I find that these same rewrite rules do not work here. For the record, the following is exactly how they appear both here and on the old web server, where they work fine:
RewriteEngine On
RewriteCond %{HTTP_HOST} ^softblackstars\.org [NC]
RewriteRule ^/(.*) http://www.softblackstars.org/$1 [L,R]
The only difference is that here they are in .htaccess in the root directory of the site and on the old server they were in the Apache config file itself (I administered the machine myself and had the luxery of modifying the main server configuration). I have verified that no rewrite rules are working; the problem is not isolated to the HTTP_HOST example above. The rules tested all work fine on other systems. Adding RewriteBase (required for some per-directory rewrite rules) does not help.
DH support, while being extremely helpful otherwise, was unable to offer any suggestions on what the problem might be. This is a bit of a problem for me, as I’m currently developing a site that relies heavily on mod_rewrite. Not finding an answer to this problem will prevent the site going live without major modification (that I’m not particularly willing to do).