I do not know if that option is available.
According to the rules of the forum, posts commenting something about a book after it is released should be spoiler-tagged for around a year. But it is true that perhaps not everybody will obey said rules. Traditionally I stay completely away of the forums until I finish reading the books, but if you are not planning to read it soon after the release, I would recommend at least stay away of the DF Spoilers section. I hate to be spoiled. In my long life in the forum my main problem with moderator was about my anger about being spoiled (an admittedly minor thing).
Unless I am very confused, Posty McPostington is a category in the forum, not an user.