Unfortunately I actually do have some trouble understanding it as well
For normal posts and impressions from a normal user you're right there is nothing wrong with not having perfect English, there are tonnes of users who do not use English as their primary mode of communication and we cannot expect everyone to have perspective English.
However, the point he is trying to make is that if you choose to try to start writing up proper reviews then it would be best for someone to help proof read and help with the grammar. Nothing wrong with that. Look at rudi for example, English is not his first language, and in his usual posts you can clearly tell that his English is not the most grammatically sound. Nobody complains. But when he posts reviews on head pie, expatinjapan or someone else clearly helps to tidy things up on the grammatical front.
Again don't get me wrong. I'm not saying anyone should stop posting or stop writing reviews if they cannot write perfect English. All I'm saying is that if you choose to publish proper reviews on review sites, it would be best to get a little help on that front.