Both of those points were actually covered in an earlier blogpost that was linked in this one. It talked about how the new contributors often have an incentive to make a quick easy fix to solve their problem while the established developers have a bunch of rules, often unspoken, that they use to try to keep the code base maintainable. If you just take in any old code, you run the risk of making the code harder to work with or alienating your developers who spend time cleaning up the code. If you dump a bunch of rules on the new contributor, you run the risk of making them feel unappreciated with your "nitpicky" feedback.