I think it could be helpful if the peers have similar or higher level than me on writing.
I think sometimes even readers at a lower level can help us to improve our writing. If it's not clear to them, then we haven't communicated effectively.
The IELTS question used to mention something about "Write a report for a university lecturer." It doesn't anymore.
It now just asks you to write with examples from your experience. There is no need to imagine that you are writing a formal paper for Oxford or Cambridge or Yale. Just write clearly and simply. Simple writing does not mean easy writing: there is a huge movement aimed at making business writing (bank letters, contracts, letters from telephone companies, etc) clearer.
One approach that is sometimes useful is to imagine that you are writing for your nephew or younger sister or brother. They are studying English, but are one or two years behind you. If the ideas in your writing are not clear to them, then you have not succeeded in writing clearly. They might not understand all the vocab, but they should be able to get the ideas and to see why you have organized the essay the way you have.
Some people think you need to dazzle the reader with complicated sentences and vocab. I don't think so - if you can use simple structures well, that's a better indication. It's hard to write simply!
I agree it's may be difficult for weaker readers to comment on what is wrong with our essays or say why our essays are hard to understand. But if someone tries and honestly can't understand our writing, then it's our responsibility to make our essay simpler.
That's why I think almost anyone's input is useful in the forum - not just 'better' writers!
It's a bit like being sick - most people can tell when other people are sick. Perhaps only a nurse or a doctor can tell exactly what's wrong and suggest a remedy, but you don't need to be a medical professional to see that there's a problem!
What do you think? How do you feel when you read over-complicated or unclear writing?