Your lack of reading comprehension.
Comprehension doesn't mean speed. Maybe he's just a really slow reader with excellent diction.
Where do you get "speed" from? That comment refers to understanding. People who fail to "understand/comprehend" usually give up reading after 2seconds....hence it was a justified remark.
You however incorrectly assumed he meant how fast a reader the poster was (most probably due to the added time element of 2seconds in the original post) then theorise about how he may be a really slow reader with excellent diction......which is highly improbable since highly literate people don't navigate to stories then "give up" reading with perfect diction after only two seconds