My humble suggestion(s) to make "favorites" more useful (and hopefully more used):
1. add the ability to "favorite" from the front page. I rarely "favorite" anything, because I grew accustomed to using "upvote" as the mechanism to save stories. I would switch, but that extra little bit of friction of needing to click through first, means I stick with my old habit.
2. Add "favorite" for comments as well.
3. (maybe) - consider renaming "favorite" to "save"? Possibly people who are used to seeing the "save" link on Reddit would find that more intuitive.
I'd cast my vote for promoting it more, it's a pretty handy feature (at least for comments)... I also like that it lists things in the order of recently favorited rather than chronologically.
For now, I have a bookmarks folder for stuff like this.