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
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)