This is 404 for me, but I found https://anniecherkaev.com/2017/06/07/System-Testing-Compiler.html
The site has a bad rel=canonical and Lobsters followed it. The author has no contact info or links to other online presence so there’s nothing to be done.
Modify Lobsters to not follow rel=canonical unless it can resolve a page with status 2**?
Good idea, posted an issue.
Compilers have the nice property of being essentially a pure function with few inputs and one output. This makes them really pleasant to test end to end.