That is why I said that there are different ways to communicate with people other than PMs. One would be through Contact tab under the user profile or any other way that you find it useful. Blocking those people won't stop them as unfortunately they will come again under new accounts and continue what they were doing before.

I noticed under the classifieds that most people are supplying their contact information such as mobile or e-mail address. There is also 'Write To Author' option which should be working under the classifieds as well as it is available only there.

Some people will come to say: Simply read those, ignore them, delete them. I know that they can do that, but how can you ignore the feeling that you've been insulted, hurt by someone that you don't know what have you done to him/her to deserve this? Believe me most of those PMs are not acceptable at all.