The main reasons that turbocharged engines are sometimes less reliable
than NA ones are that the BMEP, the average pressure in the cylinder
is higher.  This causes a higher loading on the crank journals and
main bearings, and on the pistons.  Second, more energy is being
released in the same volume.  Since not all that energy is converted
to mechanical work, more heat is liberated in the same volumne.

If the engine is not originally designed for supercharging, then these
mechanical and thermal loads create more stress that can shorten the
life of the engine.

If, as in large truck, locomotive and ship diesels, the engine is
designed from scratch for turbocharging, then the reliability is not a
problem.

Even if the engine is designed for supercharging, if it is modified so
that more boost is delivered to the intake than designed for, the
reliability is again a problem.  A good example is WW2 aircraft
engines used in unlimited hydroplanes and air racing.  The blower
boost is VERY high compared to design values, and these engines do not
last very long.

BTW, there is little difference in these effects between mechanical
supercharging and turbocharging.

What is a ppl?  Polymorphic Programming Language maybe?

More power translates to greater wear on otherwise comparable
engines.  See disadvantages below.

More power.

More power translating into increased wear.  Increased fuel
consumption.  Having another component that will require maintenance
and eventuallly wear out.

As you would with any oither engine.  Frequent oil changes, normal
maintenance, fix problems as they occur and keep your foot off the
floorboards.  If you drive normally you should not notice the effect
of increased wear.  But with all that extra power underfoot it will be
tempting to do otherwise.

depends what you mean. if the engines are exactly the same in every
part except one is turbo or supercharged, then somewhat obviously, the
non turbo/supercharged one will be more reliable, both because of
having fewer parts as you say, also as a result of having to handle
less power.

if you have badly designed engines of both kinds, I would say that the
badly designed NA engine probably would be more reliable, for similar
reasons.

but a well designed turbo/supercharged engine can be just as reliable
as a well designed NA engine. it will probably need to use higher
quality parts, but on the other hand it will be smaller.

advantage of supercharged engine is, it's smaller. advantage of turbo
engine is, it's smaller and more efficient.

especially for turbo engine: change the oil frequently. don't push the
engine beyond its limits; particularly, don't hammer it when it's not
warmed up, especially if it's got aluminum head and/or block. (goes
for NA too, but not as much). main way to keep engine in good
condition, is to buy well designed engine in the first place.