The humour barrier on here is quite astonishing at timed, the amount of times a clear and obvious joke is taken seriously...

Kind of sad, really...but you have to write "This is a joke", or "Joke Joke Joke" on some of your joke posts if you don't want the mentally ill folks to become offended. They will still be offended, but if you post a sign TELLING them that it is a joke, they won't explode into their mentally ill rants.