The tail-docking issue all got very emotional in the 70s and 80s, when some breeds, many of them by then non-workers or which, if they did work, did not work in environments where they were at risk of tail damage, were having their tails docked very very short. Vets were unhappy at 'mutilation for fashion' - we'd outlawed ear-trimming in this country decades earlier. Also, where the tail was docked very short, it was a medical issue; the muscles around the anus didn't develop sufficiently and caused such dogs subsequent problems, including anal gland blockages, etc. I think there could even be nerve damage, and certainly considerable pain, when the tails were docked so very short, too.
At the time, the KC appeared to be dragging its feet. Apparently the issue was that there were no words in the breed standards of docked breeds for what tails should look like!
Since then, the KC have updated the relevant breed standards and now, in theory at least, a tailed dog should not be penalised for carrying a tail in the show ring. Indeed, I think it is now an offence to dock the tail of an animal where there is no medical reason, so dogs which are purely for show should now be tailed. And all breeds (I think - someone will tell us if there are exceptions) are now docked with sufficient tail length that the anal musculature develops properly.
The grey area is dogs which either don't work (companion dogs) but which do run about in the country, and because of their breed are likely to run through undergrowth, and dogs where the docking cannot really be justified on the basis of potential damage - smooth coated hunting dogs, and dogs which don't hunt, for instance.
Personally I think I would dock a dog with a highly feathered tail where it is likely to spend quite a bit of time running about in gorse, brambles, etc. But frankly I'd prefer the breeders to be breeding out the feathering which is causing the problem, and working towards not needing to dock.