I think it's a matter of writing style and what kind of effort you put into making your words more... lively. In an RP post, I tend to just throw down what I'm imagining at a time, without any proofreading to consider the strength of descriptions and strong cohesion. Otherwise, I would proofread the post a minimum of six times (necessary for me to even begin to like my writing), and it would take far too long for me to get things done. So I may well be someone with the same problem.

I think it's acceptable and fairly frequent for casual. I simply use the words others write to form an image in my head of the events, so I usually just make someone's writing style work even if it is lacking  in good details, structure, word choice (like mine? :p). Can't speak for the advanced forum.