Knowing C may help me distinguish "sabotage" from "bug fixing", what you are not trying to do!
Remember that if "something works" it doesn't mean "it's right"!
Maybe reiser did mistakes writing the code; everybody (even the best programmers) make them! So, even if something works in some cases it may not work in all the cases. A better implementation could be even different.
Except if you really know what every single line of code of Reiser4 does, you should not base your sabotage theories on "lines swapped".
Ok, there may be breakage between the two different implementations, but Reiser4 is not in feature freeze! so breakage is likely to happen and you are advised that this could be dangerous for your data.