How to find all postings of a user in a board like the Options board? Is this not possible? Update: Just figured out: by going to the board and searching for "" by the user, ie. just leave the search field empty, but specify the user, and enable "Search this forum only".
Another way is clicking on the search box at the top right and then click the button labeled "More". That will take you to the advanced search page where you can select which forum(s) you want to limit your search to.