The honest answer is probably that most people are not used to having substantial amounts of fiber in their diet, and being in the form of a liquid makes it much more noticeable if you do have any issues.

The basic issue is that, while you may have gas as a result of eating a burrito, it's spread out over a day. With Soylent or any liquid nutrition really, it hits you over 1-4 hours. Ditto any other sort of gastrointestinal upset - what would be subclinical with solid food and a day or two long timeframe becomes an immediate crisis where you'd better find a restroom in the next 10 minutes.

So why aren't the competing products I've tried / researched, not filled with so many of the common complaints that Soylent has? For example the one I use is entirely flax/hemp/sesame/rice, that's about as fibrous as they get.

This sounds very anecdotal -- can you direct me to some of the products you've researched? Maybe we can do a side by side comparison of ingredients

The one I'm currently using. http://www.spacenutrientsstation.com

I would guess that competing products aren't as widely tried and/or aren't as closely connected to an online-savvy community.

Yeah it's gotta be a sample. A great many more people have heard of or used soylent than its competitors

This article is referring to solid food, to be fair

Having read about it more, I suspect that people are eating it too quickly and with insufficient liquid.

I've experienced this problem with other nutrition bars - when I eat them like candy bars, they sit like a leaden lump in my stomach for hours.

Hard to say, but I'd guess that partially it's availability bias. Problems with other niche foods aren't usually posted on Hacker News. They also don't have their own Reddit group and fans who post about each others' experiences (sometimes negative).

Plausible.

If they've really put so much science into the formulation, shouldn't crop-dusting index (CDI) be one of the metrics by which the formula is optimized?