I'm just change averse :)

We have traditionally been very cavalier in the Haskell community about gratuitously changing APIs in ways that break user code, and in my opinion this is very bad and creates a perception for users that choosing Haskell is just going to end up creating work for them. In this regard I think it's very good to be conservative -- this function has been documented to behave in a certain way and you can be sure that somebody, somewhere relies on that behavior.

Normally I argue strongly for this perspective (because it feels like few people do) on less serious things like changing function types or names, because those things break builds and cause people to scramble to restore their libraries to compatibility all at once after the GHC release. The consequences of this particular change, however, have the potential to be a lot worse than just making busywork for people: programs will silently continue to compile and then start deadlocking in mysterious (and likely rare/"race-condition-y") ways.

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