This would be a really cool idea. Like, on Discussions you can up-vote and down-vote if you like or dislike something, you should do this on people's profiles as well.
For example, if someone helps others solve problems and is helping the Brilliant Community, you can up-vote them so others can see this person is trustworthy.
Likewise, if they are spreading malicious content or intentionally giving false/misleading info, you can down-vote them.
Or maybe you could make it so there's only up-votes, to show who is truly helping the community.