But how do you measure that quality? Based on amount of contributions? Based on +1's they've received on comments?

Based on lines changed, merge requests accepted/rejected, etc etc.

You know, GitHub developers are quite smart.

They could just write their own weighting algorithm if they wanted to. :-)

Those are absolutely awful metrics to use when measuring a developer's ability and talent, or the quality of this developer's contributions. They are also extremely easy to game, too.

Yes, that's why I trust GitHub to come up with a (proprietary, unreleased) algorithm a la PageRank that won't easily be game-able.

That is truly an excellent idea. Comments like this remind me why I love this community so much. Thanks for sharing!