Fun fact: even theorem provers have counterexamples
- Breaking Badfny: https://www.reddit.com/r/Coq/comments/x4d31y/breaking_badfny...
- Falso (Coq): https://github.com/clarus/falso
- Coq critical bugs (some of these mention potential ways to prove false): https://github.com/coq/coq/blob/master/dev/doc/critical-bugs
(You can also get the theorem prover itself to hang or crash; if you work with theorem provers often, you'll even do this unintentionally, many times!)
I believe this comment is meant to be a response to another post (https://news.ycombinator.com/item?id=18155410) who pointed out a flaw (now fixed) in Coq that allowed false theorems to be proved.
Github link:
Even coq have had its bugs where it was possible to prove that true is false: https://github.com/clarus/falso
Is the Coq bug you're thinking of this one, from earlier this year?