My point isn't that it's impossible to analyze. It _is_ impossible to analyze without the context of all of Twitter's other services though. Twitter are not going to open source all of their services.
I agree. I doubt the Twitter moderation system is more complicated than the Linux kernel or any of the open source compilers. Sufficiently motivated individuals contribute, find a fix bugs all the time.
Open sourcing algorithm or code is not about everyone go and analyze the same, instead when controversy or issues arise it'll be readily available for independent experts to review it.