The torque converter in a "standard" automatic transmission does the job of a clutch, and it doesn't really wear out in the same way as a clutch does - a clutch is two dry pieces of material holding each other through friction (kind of like 2 sheets of sandpaper pressed against each other), and each time the clutch is slipped those surfaces rub against each other instead of moving in sync, causing that grippy material to be slowly worn off. In a torque converter, you have something somewhat similar to a turbine with a fluid solution inside of it - the "friction" is the turbine blades against the fluid it is filled with, instead of two surfaces contacting each other. This doesn't cause the same type of wear because the surfaces aren't abrasive against each other.
This is part of the reason automatic transmissions are kind of common in drag racing - in automatic cars, you can abuse the torque converter by stepping on the brake AND gas, up until the point where the torque converter stops locking up. This is generally around 2-3k RPMS, which means when you let off the brakes, the car launches in a more favorable position of the RPM range. You could also do this in a manual car (slip the clutch as much as possible) but you would be absolutely destroying your clutch, similar to holding a car still on an incline via the clutch. Anytime that you are applying more power than you have wheel movement means that the clutch must be slipping, and that means those friction plates are rubbing against each other instead of moving in sync, and therefore are wearing away. So you don't really have to worry about wearing out a torque converter from slipping/engine braking.
EDIT: to answer the question more clearly - the torque converter in an automatic transmission doesn't operate the same as a clutch. But you can still brake and operate the clutch on a manual car as well (heel-toe shifting, check my comment below) and it isn't "good" for the clutch, but is a valid driving technique, and as long as it is executed properly you shouldn't be putting much wear on your clutch anyways while downshifting.