I see this as two questions -
1 - Do you physically clip the seam allowance?
Only on curved piecing and only if absolutely needed.
2 - Do you clip the threads at an intersection to swirl?
Always - especially if I am doing pinwheels. As I do my own LA'ing my machine is very susceptible to bumps. I am not computerized so when I hit a bump I tend to jerk and end up having to rip out.
I too started my sewing on clothes (lots of clothes for many many years). The difference I see - imho - is that in quilting you have the added support of batting, backing and quilting to support and fortify any thing that you have done with the seams. Those fortifications are not there in clothing construction and the clothing seam must stand on its own. So I think that the clothing seam has to take much more pushing and pulling than a quilt seam. Therefore I am very conservative on those.