I wouldn't really consider pine trees as "cohabiting" with comfrey! They have totally different growth patterns and would seem to be in mutual opposition to each other.
As for the original posters question, comfrey dies back in winter and leaves bare earth. That is its nature, but also it's strength. The leaves fall to the ground and as they break down they enrich the soil, feeding the microbial life and adding nutrients. During the summer the dense leaves and vigorous growth shade out other species, such as grasses, that would grow. In a permaculture setting comfrey is typically grown in situations where these traits are directly beneficial, rather than undesirable.
For example:
Planted beneath fruit trees comfrey suppresses grasses. Grasses suppress the growth and vigour of most fruit trees, whose shallow roots feed in the exact same root zone as the grass. The comfrey also feeds the exact soil zone where the fruit tree roots are feeding, giving another big boost.
Rows of comfrey plants can act as barriers, or boundaries, between grass areas and cultivated garden beds. Grass likes to spread, creeping into areas of other plantings. Comfrey's ability to shade and suppress the grass acts as a barrier to encroachment from one area to another and simultaneously enriches the soil in your adjacent planted beds.
I plant comfrey along fencelines, where it does a good job of displacing perennial weeds that would otherwise require maintenance. Sheep find it palatable, and will quickly graze it down when let into an area, which they would not do for thistles, stinging nettles, and docks.
The above may give you some thoughts on how this area might do double duty for you. Perhaps by planting some fruit trees or berry bushes within it, which would grow above the shade height of the comfrey.
As a more general point, in permaculture we would general aim to achieve integration of the different elements in our design, in such a way that the whole is more than the sum of it's parts. A "patch" of comfrey sounds like it is isolated from the whole, which is why you are running into problems. In some ways I can see why a patch of it would be potentially quite useful - it could be a comfrey nursery, providing new root cuttings in a convenient single location. It might be located to make best use of a nutrient rich leeching from
compost heaps, or from an animal enclosure.
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