I strongly disagree. Where would you discuss poly drug abuse, which is the most prevalent, dangerous, and potentially lethal form of addiction? Shooting heroin with methamphetamine as a speedball in addition to taking benzodiazepines or drinking alcohol, would this go under opiates, benzos, alcohol, or where? Where would these high-risk users get their answers/input if the most knowledgeable, experienced, smart people using combinations of drugs simultaneously cant find the thread in question? How many people will receive inferior HR and lower quantity and quality posts due to bluelighters inability or unwillingness to check a dozen subforums vs just one?
You want HR information to be easy to find, one forum with everything OD in it, just a search away. With many subforums, trying to find your thread or any thread, for that matter, is much more difficult.
How would you staff all the new forums, especially when almost all of them have significant overlap, or, none whatsoever, you expect the OD mod team to suddenly patrol a dozen subforums if OD got divided? Even if they don't mind, they might not be able to enforce the BLUA as effectively as previously, and this can lead to risky behavior not getting caught in time by the forum regulars as well as the staff, bad advice with drugs could go unnoticed long enough for someone to hurt themselves.
These r a few examples of why its not a good idea to break up OD, and how it doesnt make logistical sense either from a staffing standpoint.
Dont fix what ain't broke.