I hadn't heard of Common Lisp Conditions before reading this thread, but I looked them up in response to it, and I have to ask -- what is the fundamental difference?

Granted Common Lisp is not statically typed and the type system support for effects is a major part of the utility of algebraic effects in Koka, but otherwise they do look remarkably similar to me, both offering a form of delimited continuation that allows you to write code that can call out to a non-local handler that is set up the call stack, and which can itself return control to the caller.