I've heard PG complain about using "YC" in titles (from guidelines: "In titles, please don't describe things by their relation to YC unless they're actually associated with YC.") But I didn't think the use of the word "reject" was the issue. YC even uses that word themselves in their "non-judgement" letter. ;)
"Groups we rejected will go on to create successful startups. If you do, we'd appreciate it if you'd send us an email telling us about it; we want to learn from our mistakes."
So they are also apparently are interested in hearing about such things too.
the rationale behind adding "YC reject" in the original title was two-fold:
1stly, to highlight that there are success stories amongst those who are not accepted into YC.
2ndly, to point out that not getting accepted by YC may have emboldened the founders' resolve to 'go all in' and focus exclusively to make their startup a success.
i still think the extra 'noise' was a justified trade-off, given that the original article mentioned the YC rejection as additional motivation.
They're interested in hearing the success stories of non-accepted companies, but that doesn't mean that the words 'YC reject' belong in a HN title. There are ways to communicate with the YC principals other than posting to HN.
With HN having a high concentration of people who are in some way interested in YC or its model, I'd think the success of rejected companies would be interesting to more than just the YC principals.
"Groups we rejected will go on to create successful startups. If you do, we'd appreciate it if you'd send us an email telling us about it; we want to learn from our mistakes."
So they are also apparently are interested in hearing about such things too.