Does replying to YouTube comments help a channel grow?

Yes, especially if comments are real.

not much for actual growth imo. replying to comments probably won't make a huge difference to the numbers, but it does help you get closer to your viewers and makes the channel feel more personal. people remember that kind of thing.

Absolutely conversation is the best way of interaction or engagement, so in my opinion replying the youtube comments and Satisfactory answers which solve the problem of audience or viewer can help to gain better interaction. Usually when the viewer ask about anything he saw in the video in comment section most people ignore it or answer it very late this thing hurts the viewer because he want quick reply to solve his problem. So replying comments means you importance your audience and this thing will win the heart of your viewers.

if you can keep the engagement bait active , it certainly can work in various wayss