This has been proposed on MSO over and over and over and over and over and over and over and over and over and over and over again (and possibly, even more). The answer is, ironically, always one: no.
I think this is because of the SE structure where usually one answer is what is being looked for. If you really want to give some nice feedback to those users, you could up-vote their answers and/or assign a bounty.
About the FGIW problem... It's true that the first answer sometimes gets upvoted more, but I've often seen answers being posted after the first one being upvoted much more, even answers posted by me.
Jeff has also suggested a blog post once: Mixing Oil and Water: Authorship in a Wiki World.
