I've known employers like this. I've worked for employers like this. Employers are already monitoring social media. Third party services are paid by employers to monitor for staff that might be looking at other jobs. Recruiters make it their mission to know who's looking and what employers are likely to need their services in the near future. This is much of why trust and discretion is the most important asset on both sides of hiring related activities.
Triplebyte burning down their reputation as a recruitment avenue is one thing. Locking job searchers into reputation and livelihood risks inside Triplebyte's own reputation dumpster fire, on the friday before a holiday weekend, during historic unemployment levels, in the middle of a fucking pandemic, is unforgivable. The CEO showing up in person with hamfisted gaslighting (seriously?) in the middle of this self made disaster makes me hope those comments don't get flagged out of future HN search results.
Triplebyte is a YC company and HN is a YC site, so economic interests are aligned with nuking highly critical comments
This is theoretically true, but the fact that it's been on the home page for 12 hours and has accumulated hundreds of critical comments, none of which any mod has touched, seems to (a) eliminate that possibility and (b) demonstrate that the risk is theoretical, not actual.
(Keep in mind that YC has thousands of investments, so whatever you think of their ethics or the incentives, a filter like this would be impractical and obvious. Also see "Not behaving in a way that damages the reputation of his/her company" on https://www.ycombinator.com/ethics/ - it's hard to imagine YC supporting this.)