idk if it counts as an obvious hazard, but being able to modify the original input by reference within a chain of piped functions definitely makes it a lot harder to reason about what that sequence might be doing. Particularly since we assume that arrays are passed by reference anyway unless the function you're calling is making a shallow copy of their elements.

My feeling is that this makes the code less legible. I'd rather write 5 lines of code that mutate an object or return a copy than do a pipe this way. I'm sort of not excited to start running into examples of this in the wild.