If I may. My only confrontation with Jap knott weed was during my employment at Rushgrove House in Woolwich. It was a MOD property and the home of the Garrison Commander. In the grounds a large lake/pond was a feature. For the carp fishermen, it was the tops. Apart from that. As I had experienced, the MOD were not in anyway big spenders when it came to residential gardens. Likewise the residents were here today and gone tomorrow, so why should we fork out on the garden.
Using Google Earth. The garden at Rushgrove can be seen. At the bottom of the garden next to the pond is a wall. At the corner of the wall is/was a clump of Jap:Knot Weed. During my stay at Rushgrove. I never detected any wandering etc of this plant.
This here and now leads me to suspect that, yes this plant can become invsive and if located close to buildings etc, may cause structual problems. I am of the mind that. Leave it alone. The moment you interfere with it, then it will hit back.
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I live in west central Scotland - not where that photo is...
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.