Bluelight isn't more restrictive, it's more real.
For instance, closed discussions are closed for a reason, Bluelight has a very straightforward and realistic set of rules, available in the FAQ at the top of your screen. Bluelight also is very aggressive (as it should be) against trolling, something that's very hard to find on message boards these days.
Bluelight also doesn't use the term "SWIM" or variations thereof, because, to be perfectly honest, "SWIM" is stupid. Everybody reading your post knows its you, and it makes reading threads extremely hard.
Bluelight has a much better flow, I think, for the sole reason that we're not using SWIM, SWIY, etc. like other drug forums do.
I don't think heroin or opiates are downplayed at all, look at Other Drugs and Basic Drug Discussion...there's threads about opiates all over both of those forums.

Just because there isn't a "opiates discussion" board doesn't mean people on Bluelight don't use opiates or heroin