Working for YC startup, afraid founders will badmouth me at YC if I quit

Find a new job first, then quit.

I am not part of nor associated to YC but I wouldn't worry about this, good YC founders know there are bad YC founders (same for techstars etc) -- FWIW I have worked with YC founders. Being in the "club" doesn't mean you are necessarily "good", just means you passed a bar that YC thought they could make money on that served a need. That isn't a dig at YC or any other accelerator, it is just how it works.

If they speak badly of you it is more about them than you, and it might work once but if they going there it will backfire on them. Plus there are 100's of other startups outside of the YC ecosystem, look at those if you are worried.

I also left my startup due to ethical concerns. First, keep in mind that if they are this disorganized and vengeful, people probably already know and will sympathize with you. Second, if you're not a founder and didn't work there long, you can leave it off your resume. Third, if they do badmouth a fresh employee, I think that's a reflection more on them than you. Hearing that you left a startup quickly would mostly make me wonder why rather than assume anything about you.

I know it can be scary especially if they lie about you behind your back. However, people gossip unfoundedly all the time, and there isn't much you can do about it except continue to be a good person. As other commenters mentioned, the tech world is large and the vast majority of people you talk to will never hear or care about the gossip.

Remember, YC and YC startups are actually a VERY small part of the world. It's easy to fall into YC-myopia when posting/reading on here all the time (especially if you live/work on the West Coast, particularly in the Bay area) but there's a much, much, much bigger world out there.

Of course, you might have to ask yourself if you'd ever be OK working for an auto-parts manufacturer in St. Louis, Missouri, instead of a super-sexy "web3" SV-wannabe-unicorn "hot startup"... But seriously though, there's more to the world than that little bubble.

I was also "threatened" by a company in the bay area (not a YC company, but a company backed by a very large fund and the company is currently a "unicorn"). The founders also threatened me with things like, "It's a small world out here. Everyone knows each other in the bay area. Your work will follow you forever."

I ended up leaving the company after a massive shouting match with the CEO and nearly a first fight.

No one has ever heard of this story and it has never followed me anywhere.

Are you a slave that you can't quit even when you want to? What they do is their responsibility, grow a spine and quit.

Unless it's a very particular scenario, I can't imagine your ex-employer bothering to take the time to bad mouth you in any way that matters.

If your fear of these people badmouthing you is at the top of your worries - your problems absolutely don't end there! It's not like the entirety of your presence is their startup's core competency. Just leave formally as you should and part ways like adults with different things going on with your lives. I wish you the best.

If you're not a founder or hold a sizable stake in the company, it doesn't matter and anyone at the company telling you different are lying to you.

You're expendable. That relationship in the current market goes both ways.

Hope you find what you're looking for in your next role! Startups vary greatly.