It's impossible to delete all spam, just like it is impossible to keep your promise, unless you leave, but that's not my intention at all.
Why is it that when you start a thread you think that you're somehow the owner of that thread? It just isn't true. And if you insist on having no spam nor flame (which should be removed/edited, yes.) in your threads, you could always PM a moderator to ask if you want your topic closed, because your question has been answered, and there is nothing else sensible to say in your thread anymore. End of problem?
Btw, this is severely off-topic... any questions on issues like this are best kept in a PM to a moderator.