—> They thought that in xix century using certain substances would have sound exotic, but it’s not anymore like this nowadays, so they decided to make him having a history of drug use but recovered, because it would only sound stupid for him to be a junkie. Bye :-)
Ah, the hazards of a long-running conversation with a lot of different people at once.
They did discuss Sherlock’s past drug use in the A Study in Pink DVD commentary as you mention. (Several times, in fact.) Moffat and Gatiss also talked about it in an interview I’d linked to before.
In the post you quoted, though, I was trying to say that they haven’t directly stated that Sherlock has a history of drug use within the episodes as aired. Sorry if that was unclear.
Now if we get into the unaired pilot, they were much more direct:
Just one of many things changed between the two versions of A Study in Pink.