For this specific HN post, speedrunning is a bit of a misnomer. He used similar tooling to effectively add support for a physical keyboard and additionally a bunch of keyboard shortcuts that are capable of inputting custom text, songs, and fabric patterns.
There's a YouTube video where the author showcases this. It's pretty short and a really interesting watch: https://youtu.be/Yw8Alf_lolA
I 100% agree with the idea that rap is certainly not the only genre to glorify violence, drugs, etc. But the specific song choice is not really a great example in my opinion considering the last verse is
This song always struck me as a cautionary tale. Nothing about the song really seems to glorify the behavior.