I have always felt resteems were underused here. They could easily be a much more useful and interesting way to build a trending algorithm than payout/velocity as the current steemit trendalgorithm is. Resteems by someone who doesn't resteem much could be weighed more heavily than resteems by someone who resteems everything in sight as a ferinstance. And of course comments could be used in similar fashion as part of said hypothetical alternative to current junk trending algorithm.
I actually approached steempeak team a while back with a feature request that would have been basically the opposite of the currently available "exclude resteems". I asked if they could add a feature to the feed where you could only see posts that had been resteemed in your feed. They didn't think anyone would use that feature, but I personally think it would be a super useful way to find content by people you weren't already following.