Yeah same here. Sketch is a pretty widely adopted tool in web development so your audiences will very likely overlap.

I would re-consider the name sooner than later?

That was my initial reaction as well.

Yup.

We thought it was such a different product that people wouldn't be confused at all. But if it turns out to be a problem, we'll figure something out. Thanks for the feedback!

How will you know whether it's a problem?

It sounds like you're turning a deaf ear to the fact that it is a problem. Both apps are used for designing applications (even though the functionality and what kind of design is different). I wouldn't be surprised if your mentors at YC have already advised you to change the name. And more people in this thread have commented on the name issue more than your product itself. "If it turns out to be a problem"- It's a problem alright.