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In addition what Evgeny said I'd like to add that at least some of the pull requests look 'invalid' to me. At least one is clearly superseeded by an updated pull request. Another one just replaces 'karma' with 'reputation' without justification or backwards compatibility.
I suspect at least 1/3 of the pull requests is invalid but still a lot of developer time wasted. Probably you could get more useful contributions if you (Evgeny) had the time to share you thoughts/critic on the pull requests.
It might also help to have a publicly available continuous testing server (prominently displayed) so developers will be more aware of the testing requirement.