Submission guidelines state that a submitter should submit their site ONCE to the SINGLE, MOST APPROPRIATE category. Exceptions include sites with a Regional component (submit your Widget company to Business/Manufacturing/Widgets and Regional/United_States/Iowa/Podunk) and sites in multiple languages.
Editors, however, can and often do "deeplink" sites that are of particular usefulness. The guidelines for deeplinking are publically available at
http://dmoz.org/guidelines/site-specific.html#deeplinks .
The list you provide is misleading. Most of the top 20 are free web hosts (Geocities, et.al). They have thousands upon thousands of unique websites that just happen to share a domain name.
The original post in the thread you cite is incorrect in many ways, not to mention libelous. There is no editor that can effectively keep sites out in ANY category. No editor OWNS a category. Maybe he should come here and ask for a site status.
And, I'd like to add, we take allegations of abuse very seriously. If he submits an abuse report with the "evidence" he claims to have, it WILL be investigated.