I don't think it blocks PMs, but if you're getting unwarranted PMs, ask the person to desist from sending you PMs, and if they continue to pepper your inbox, feel free to forward the relevant correspondence through to staff for review.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)