I think lots of us have had the odd frustrating conversation on here, where the other person just hasn’t seemed to be able to grasp what we’re saying. Apparently, it’s very possible that the posters in question genuinely don’t understand.
A 2011 government survey of adult literacy skills found that 14.9% (or 1 in 7) of adults in England have literacy levels at or below Entry Level 3, which is equivalent to the literacy skills expected of a nine to 11-year-old.
More recently, in 2015, the OECD conducted its Survey of Adult Skills, known as PIAAC (Programme for the International Assessment of Adult Competencies). This survey found that 16.4% (or 1 in 6) of adults in England, and 17.4% (or 1 in 5) adults in Northern Ireland, have literacy levels at or below Level 1, which is considered to be 'very poor literacy skills'.
More info here, if you’re interested: literacytrust.org.uk/parents-and-families/adult-literacy/what-do-adult-literacy-levels-mean/