I’d like to point out an example scenario which demonstrates the utility of assists. In this question, I asked for help to correctly get a command-line argument. The two posted answers were not useful, but the two comments (to the question itself) did give me a nudge in the right direction. As a result of the two comments, I did some testing and found the solution myself. I figured the correct action to take was to post the final answer myself since none of the existing answers were applicable. However, the most that I could do to credit the two people who helped (ie assisted) was to up-vote their comments.
I believe that an assist feature could be helpful in the this situation—like ExpertsExchange has—(though I’m sure that someone can probably explain why even in this scenario it is unnecessary).