I have never grown comfrey, but have many heuchera in different flower beds.
I tried two years in a row to start it from seed, as I have a greenhouse and can get a good start on perennials. I start many different annuals, perennials, herbs and vegetables....and coral bells do not germinate well. Wasn't worth my time, so I buy the smallest plants I can find as early as I can find them, and keep up-planting them until they are a good size to put outside.
you may have different luck than me at starting coral bells from seed, and if you do, please let me know the secret.
