The worst I've seen is a recruiter that didn't tell me I had been accepted. I found out when someone at the company followed up on why I hadn't responded to the offer.
I have no idea how a commission-based business manages to do something like that.
Are internal recruiters (sales people) commission based? Seems strange.
No, but lots of firms (this wasn't Amazon) hire external recruiters who are commission based, usually a percentage of salary for each candidate placed. Some also get "right to represent", where you can't apply through the employer directly once you've started a process with the recruiter.
Which makes this utterly weird - it was literally a matter of giving up (potentially) several grand by not forwarding an email.
Some claim it's them covering their ass thanks to the SUE SUE SUE culture of the US.
I understand that, but when it's a purely technical decision they could easily enough give you constructive feedback.
You missed these two edge cases. Your code crashes on certain inputs. This is very inefficient, you could have done XYZ.
You could automate chunks of this, and protect yourself from any discrimination lawsuits by just making any engineer who reviews the code have zero knowledge of the candidate.
That's pretty common recently for companies. I'm not sure why.