-When browsing through someones posts I'd like it if there was a sorting feature so that I could select a specific board and see all the posts the user has made on that board.
Since we don't have that you can always use the browsers search option. I am sure you know that but lets say you want to check only posts on Meta - hit CTRL + F to open the search tab and enter Meta in it. All the words on the page containing Meta will then be highlighted. But you still have to browse through all the pages manually. 