I know very little about opiates; one of the few things I know is that there seems to be a broad consensus that this is bullshit. I don't remember if it was bluelight or somewhere else, but I remember coming across a really lengthy thread on this subject, with a few people insisting that it produced an effect, despite total dismissal from everyone else. Some people suggested that if there was an effect, it was a placebo effect. I thought the discussion was kind of fascinating from a psychological standpoint.
My theory on this, based on the nature and flow of the arguments in that thread, is that loperamide is an especially effective placebo because it is not only active (in that it produces noticeable effects on the body, unlike an entirely inert 'true placebo' e.g., a sugar pill), but it produces some of the same effects in the body that centrally active opiates produce -- specifically in the bowels. Addicted minds are particularly good at noticing connections and relationships between things. The expectation that it may be centrally active, either because it is being taken as a mega-dose, or combined with some other compound believed to help it 'cross the blood-brain barrier' or the like, in combination with physical effects that are also produced by centrally acting opiates, work together to induce a particularly effective placebo effect.
That doesn't mean it isn't 'real,' of course; obviously, like every other mental experience or act, it has an underlying physiological basis. In some cases, the placebo component of the response to an opiate explains as much or more of the variance in the subjective effects as the direct effects of the opiate itself. But I suggest that a) it is unlikely to be effective at all in a non-addict who is trying to use it to get high; and b) the mechanism is not what it is purported to be.
I'm not familiar with studies on the effects of loperamide, so you can take this all with a grain of salt, but I am extremely familiar with the literature and current research on the placebo effect.