I'm not necessarily of the opinion that a rep / thumbs up button would be beneficial to felicifia. The main advantage is that it would encourage posting. However, I feel that we already have the utilitarianism group on facebook. The main advantage of the forum in the first place is that it injects some degree of class.
I think ultimately, if felicifia wanted an upvote system, it would make sense to start a proper group blog, like 80,000 Hours, and like the Lesswrong Blog. In fact, I would argue that if someone has some work that they are particularly proud of, the Lesswrong Blog and 80,000 Hours are already good places to have their ideas tested.
Creating a rep / thumbs up button would take a fair bit of work to find, implement and maintain.