Geoff Dann, you have entirely missed the point here. Conversations like this often crop up ... (just the other day, we had one about the advisability of wearing cotton clothing in the cold and wet) ... where specific instances of something, which are fine in themselves, run counter to more generally accepted wisdoms.
Sometimes wearing cotton in the cold and wet is fine, but usually one advises against it, right? And, if someone posts about wearing cotton in the cold and wet, one would want to see someone mention the potential pitfalls of that. It is the same here. Members are just putting into this thread some reasonable and responsible cautions about pond flora and water sources so that, having read your informed and informative article, other people don't then just go blithely down to the canal and scrape whatever greenery they find sitting on top of it to stir into their fried eggs.