First, a user should have the choice if he allows comments on his wall or not and by whom. It could be nobody, everybody, accepted followers or mutual friends solution. See as well my detailed answer on page 4 of Your 1.6 question.
When writing on another users wall, one should have the option to decide if the comment is public or private, the receiving user could have these marked with green and red colors for example when seeing his wall.
Second, a report button shoud be core from the beginning on, otherwise spammers will post on profiles with low activity.
The more core the better, for some important plugins people are waiting two years, that is too slow.