I think at least part of the solution should be replying to all such instances with "Hello your client is broken. Would you mind using a different client." It'

I think at least part of the solution should be replying to all such instances with "Hello your client is broken. Would you mind using a different client." It's a ridiculous and easily dismissible statement at first, but not so ridiculous if it becomes commonplace/familiar/canon (it worked for internet explorer!)