I think I understand where you are coming from, but I don't think
your observations apply to everyone.
I routinely solder all jump rings, even on 1.5 mm bead chain
If it is fine you will need a fine jump ring and then it should be
soldered, plus the heat is seconds fast and concentrated, so you do
not need to treat the metal and can protect fragile areas from heat.
Pendants also need to be soldered unless you have a reason not to
because they weigh in the bail. Also most pendants can be fitted
over the ends or they can be hinged so the soldered join is very
easy to isolate.
I doubt that a customer who had spent $50 on a sterling chain which
was lost... Perhaps the jeweler who said this meant that he did not
get enough value for the metal to warrant the extra time, which
sounds like a pricing problem to me, and a lax attitude to customer
I agree. Leaving any piece of jewellery so weak that it WILL fail is
bad regardless of cost.
However, if it is going to fail and the place can be planed but
leaving a join unsoldered does the job, then that is a good thing.
Leaving a week point is not usually the plan but I can think of a
few reasons why you should. It can be helpful if you are polishing a
fragile necklace; if you let it go, neither you or the chain will
get hurt. It doesn't always pay to solder everything at once in some
fine pieces which need polishing before complete assembly.
A lot depends on aesthetics and it depends on style.