It's because this link (https://github.com/phoboslab/qoi) has been approved by mods for reposting: it appears on the "pool" list [1] [2]. Which is a bit odd because as you point out, a different link [3] for the same project already received lots of attention.
[1] https://news.ycombinator.com/pool
[2] https://news.ycombinator.com/item?id=26998308
[3] https://news.ycombinator.com/item?id=29625084