On their profile page click on New Wall Post. You can then post a message to their wall.
I know this is an old page, but it’s the most relèvent I could find to my question.
I get “there’s a limit to the number of posts you can make, please try again later”. It’s only on players profiles and I have posted on them but not a lot and certainly not recently, about 1-2 in the past few days.
Do you know the limit or where I could find this out?