It can get quite ridiculous... How many published patterns have we seen that are nothing more than traditional blocks given new names? Sorry... I don't respect that as someone's "original". Copyright is the right of "copy"... copy meaning the actual written words. No one has the right to take your writing, the way you explained the making of the pattern. However, making a "knock off" of the original design from pictures is fair game. It's the reason so much of the fashion world is 'knocked off'. The law does not prohibit it. Books, written patterns, song lyrics... all that "copy" is protected. Actual designs, not so much. However, an ethical person would give some sort of credit to who or what ever inspired their creation.
I am a knitting pattern designer. How I wish my actual designs were protected from being copied. However, it is only my written words-- the way I explained the instruction-- that is protected under copyright law. And even that is only enforceable if you have the money and legal representation to sue those infringing on your rights.