From that exact link:
“Diacetylmorphine was first synthesized in 1874 by C. R. Alder Wright, an English chemist working at St. Mary’s Hospital Medical School in London. He had been experimenting with combining morphine with various acids. He boiled anhydrous morphine alkaloid with acetic anhydride for several hours and produced a more potent, acetylated form of morphine, now called diacetylmorphine.”
I’m saying njtt wasn’t getting high because she wasn’t trying that hard. She wasn’t taking heroin by mouth. She was taking something specifically made to be taken by mouth and for pain. Not taking it in a method specifically to get her high. She was taking it as prescribed and therefore wasn’t getting anything resembling a high.
Except that purified isn’t correct at all. It’s acetylized which completely changes what chemical it is, albeit to a similar one. It would be like saying water is a purified form of hydrogen peroxide.
In other words, it isn’t a “purified version of morphine”.
I think Diactyl Morphine was a kind of dinosaur that put its prey to sleep before killing it…
It’s important to remember also that abusers, at least the ones deliberately seeking a rush, may take much larger doses of any drug than would be used therapeutically. For example, ccording to Wikipedia, high doses of amphetamine can result in hallucinations, among other things.
You too, huh? 
Just noticed this part and had to mention how it’s very slightly wrong. There are some opioids that won’t get you high at all. For instance, loperamide is found in over-the-counter anti-diarrhea medicines. It doesn’t cross the blood-brain barrier in sufficient amounts to cause euphoria and analgesia. It only slows down peristalsis (the flow of food through the intestines).
Also, there are different types of opioid receptors and if I recall correctly, different opioids can trigger different receptors. However, as far as I know, the mu-opioid receptor is the only one that causes euphoria so I wouldn’t expect highs to vary much between different opioids. However, from accounts I’ve read, it does actually vary some beyond just intensity. Supposedly people feel more energetic on oxycodone than hydrocodone, for instance.
Hence my use of the phrase “pretty much” 
There are a couple different opioid receptors, with the mu receptor being one of the most important ones.
Though, if you want to be REALLY technically, loperamide does work the same way as most of the other opioid, it acts mainly on the mu receptors. However, due to it’s structure, very little crosses the BBB (as you mentioned), and the little that does, is actually actively transported out of the brain. It’s mechanism of action is the same, just the site of action is different.