i don't see the point of locking

You use it to "put your money where you mouth is" and boost your post.

where does one find posts ranked by boost?

there are tabs below the stream header at the top : recent , hot, top... but these need to be improved and don't take upvalue into account yet... soon tm

same with searching... upvalue will soon be used to impact search result ranking

where upvalue is defined as tipping not as locking