One of the two authors here. Happy to answer questions.
The intent was to open things but not publicize them at this stage but Hacker News seems to find stuff. Wouldn't surprise me if plenty of folks follow Daniel Lemire on Github as his stuff is always interesting.
Any chance to have a similar thing for s-expressions? I parse GBs of them and Common Lisp reader is very slow.
Probably not too hard. It would come down to how easy it is to detect quoting conventions so you don't accidentally parse () chars in strings. JSON is medium-easy. I don't know where the canonical definition of s-expressions you're using comes from (is it just Common Lisp?) so I don't know how this works.
We'd like to have some more examples of formats people care about - I'm interested in generalizing this work. So if you want to followup with more detail please do.