[mousey]

The idea is for a quick fix or a couple of days at most.
if you have no other tank to put your fish in this buys time.
the author of the thread was concerned about the fish getting cold and a 2 kg p'butter jar is not a bad size for the betta, and solves the problem of being attacked by the others.
I deal with mostly small fish like guppies and platies and this works well for me. generally a fish that is being beaten up or is ill does not want to swim around too much.
The ill fish go into a container that has no holes. Then they get their medication in the small container as well as twice daily water changes. they seem to like to see the other fish.
An aggressive fish of course has to be rehoused but as they are small fish a few days in the container with holes gives a chance to figure out the options.
it is really no different as I see it to a person being confined to a sick room.
there is certainly much more room in the p' butter jar than the breeding containers that float in a main tank, but if you don't like my idea don't use it. I only offer it as a way to think outside the boxes and to perhaps relieve the fish from some stress.
Also most of us have empty plastic containers in our recycle box that are more easily obtained at odd hours than is an extra tank.