"soft fiber" can irritate, and are soluble

Actually, the point of the original poster's quote was to reduce soluble fiber intake, and increase INsoluble. Oat bran is "softer" than wheat brand because it has MORE soluble fiber and less insoluble. (look it up on nutritiondata or any other nutrition facts site that doesn't sell anything)

Some people have too much of the gut bacteria or yeast that ferments soluble fiber in a non-helpful way, and depsite the world telling us to "eat more fiber", must do what works for them, not for everyone else.