What are the implications of changing repl.commit_order?
To my knowledge using repl.commit_order=0 may be not safe from the data consistency point of view. It is rather a variable meant for tests/benchmarks.
However, I am not able to reproduce your results of setting this to 0 leading to 10x better performance. In fact, I did not notice any significant difference on my test cluster. Can you share some details about your configuration - my.cnf and how far are the nodes from each other (network round trip)?