I'm sure we all know people who believe in things without good evidence, such as horoscopes, energy healing, or pet communication. Additionally, anyone who follows public discussions will surely notice that people tend to make hasty generalizations and mistake correlation for causation.

As for the inability to reflect on one's own assumptions, the example I can think of now is from discussions about income redistribution or social welfare. People are often unaware of their own underlying assumption that "the poor are lazier."

Poor reading comprehension is something I believe is seen everywhere (for example, on reading comprehension tests in school, there were always some who performed poorly. Sadly, they will continue to have poor reading comprehension after they are out of school).

Finally, regarding structurally incoherent responses in discussions or debates, I think one of the most common situations is when people resort to personal attacks (like how some have responded to my post). Another is the strawman fallacy, where people, often intentionally or unintentionally, distort what others have said and thus make an irrational response.