Anything that works for you is good for comics! You don't need someone to give you permission to do a thing, or tell you it's okay, in order to use it!
I use ballpoint pen to ink my comics. Literally nobody told me that that was a good way to do it (in fact I had someone scold me for it) but now whenever I show my process, I get readers who think it's really cool that my work is traditional with a kind of weird tool! It's a little slower than some methods, but I'm comfy with that, so it works for me.
So is watercolour good for comics? Well, you're already doing it, so you'd be able to say more than those of us who haven't tried it!! You have to figure out how to scan them in to preserve the image, you have to have the physical space and the physical supplies and the skill with watercolour and the control to make it work. But whether or not it works for you is up to you, not anybody else. : )