Factor supports both dynamic and statically-unbalanced stack effects, but the former risks destabilizing the runtime and the later requires that defunctionaliza

Factor supports both dynamic and statically-unbalanced stack effects, but the former risks destabilizing the runtime and the later requires that defunctionalization (read: inlining) ultimately resolve to a static, balanced stack effect. It's all documented quite well in subpages of that article I linked you to. In practice, all of the unbalanced stack-effects will become trivially balanced at word boundaries & dynamic stack-effects only occur when metaprogramming.