Hi all. I have opened two tickets on the MapRoulette issue tracker to cover two new features that are closely related. The first is the ability to “like” a Challenge, and the second is to “Flag” a challenge. Liking should be self-explanatory. Flagging is a way to signal that you think the challenge is confusing / causing bad edits in OSM.
This short blog post on the MapRoulette blog gives some background and links to the issues. If you have opinions or suggestions please discuss on the issue pages. Thanks.