Comment by koito17

The intent is to have a proof of some proposition. The Lean runtime crashing doesn't stop the lean-zip developers from formally modelling zlib and proving certain correctness statements under this model. On the other hand, the Lean kernel having a bug would mean we may discover entire classes of proofs that were just wrong; if those statements were used as corollaries/lemmas/etc. for other proofs, then we'd be in a lot of trouble.

When I see a title transitioning from "Lean said this proof is okay" to "I found a bug in Lean", I'm intuitively going to think the author just found a soundness (or consistency) issue in Lean.