I eat it whole, fresh picked as a leaf or flower. If I am hungry in the garden as a tiny snack. Or if I cut myself.
I used to use it for green smoothies, but I have gotten out of that habit.
If it's winter and I have a cut, I drink it as a tea.
If I have a puncture wound, I do not use it topically at all, but rather orally. That way it heals from the inside out. I once used it as a poultice on a deep cut, and the outside healed too fast, with the inside still lacerated.
I don't think it should only be taken internally, or even primarily. But it is fine unless you are pounding it relentlessly.
Doc Jones has pointed out that the studies with
mice would be the equivalent of a person eating many pounds of comfrey, exclusively, daily, for weeks on end. "So don't do that and you should be fine" he says.