Spelling should be a priority if you are going to post. You might be posting something really funny, but it will be lost sometimes if you spell the punchline incorrectly. Take for instance, arguably the greatest wrestling talk forum member of all time, Prant Garker. His spelling and syntax are impeccable! The hilarity of his witty banter is increased 10 fold by this. So while you don't have to write like Shakepeare to post on the forum, that doesn't mean you should write like Huckleberry Finn instead.