With Disqus, can I allow the most 'liked' or 'favorited' comments to rise to the top, sort of like YouTube? If not, are there any other commenting systems that have this functionality built in?
You can use other plugins to do this too. Here are some I can think off:
I would suggest you use IntenseDebate by Automattic which means it will always be up-to-date and most compatible with your site.