I certainly notice it as I post a lot across networks. I always have a title with my content explaining what's what. There are so many times I have to reply to a commenter, saying "yes, that was what I mentioned in the post". Clearly, way too many just dive in and comment on a title without even bothering to read the post content. It's not that the content is pages long, it is usually maybe 3 or 4 paragraphs.
It's no wonder so much misinformation takes hold, as few take the time to critically comprehend what they're reading.
I think it is partly just fast scrolling and laziness to actually read the point being made. But then you may ask, why bother commenting at all then...