Specifically, the paper does not describe the construction of a novel virus from HIV and SARS, as has been claimed by such scientifically literate publications as the New York Post. The paper describes the assembly of proteins from the SARS coronavirus and some of its close relatives, as a way of testing whether such recombination in vivo, as occurs in coinfection of a single host by multiple strains, would be likely to enable a strain previously not infectious to humans to become so. The only way such a constructed protein can in any way affect human cells is in a plate, with extensive lab support. The protein isn't a virus, and cannot become so. It's the biological equivalent of a unit test, rather than of application code.
The trouble is that you need to be able to follow the paper to understand that this is the case. If you can't, and you're already frightened enough to be foolish - or inclined to tendentiousness for some other reason - then it's very easy to incorrectly conclude, based on the 10% of the words in the abstract that you do understand, that the current pandemic is the result of, at minimum, an accidental release of a pathogen deliberately created in a Chinese laboratory for some negligent or nefarious reason.
To be painfully clear, that is false. Everything about that is false, and the paper supports absolutely none of it. But a lot of people are pointing to it as though it did, and that probably explains the flags.
Some subjects simply cannot be discussed: there is a Paul Graham's blog post about it. That is a bit sad that the moment, however urgent, dictates what can talked on a pretty harmless forum.
Which is great, because misleading titles is one of the bigger problems here on HN, made worse by 90% of people not reading anything but the title and the comments
https://news.ycombinator.com/item?id=22663029
Sometimes people see the older article second and flag it as the dupe.