Going back to the original post, I think the point was that his normal supplier has gone out of business so he will be acquiring fish from a new untrusted source.
I'm sure everyone else here gets used to dealing with certain suppliers and gain the knowledge of what they do.
On our discus tank we used to always get fish from a local guy who imported them and wouldn't sell them until he'd treated them and they'd been QTed for a month, with a money back guarantee a year after purchase, so sure he was that they were free of disease.
I would always use a QT but it depends on who you get the fish from I suppose, if a good relationship has been built up over the years and you understand what the dealer does it could be argued that it not necessary in certain cases.
Just my opinion