On every use profile page the search bar on the top of the page already contains
user:<id> text to simplify search for post of the currently visible user. But this doesn’t work correctly for the Community user:
Instead of searching for posts owned by Community user I’ve got Jeff Atwood posts:
In this case minus sign was just ignored and instead of (-1, i.e. Community user), the (+1, i.e. Jeff Atwood) is used. Same happened for any other negative id for the “user:” option in the search box.