Thanks MonicaMC again was not trying to say it was untrue just didn't know about it. I will keep looking for stuff! I always want to learn and do better so thanks for bringing it up!
Stress bars are *usually* well defined... but I have seen stress bars so bad that the feathers were a dark color, and not defined on a young bird. I'm not sure if we could still call them stress bars, as the feathers did not appear weak, but they were certainly not the right color.
And hey, it's better to ask a question and to question what you are told! I'd rather bash heads with someone over a debate, and perhaps both of us leaving learning something new rather than accepting someones word on something simply because they are an "expert" (i.e. they work in a pet store, they are a breeder, they have vast experience, etc - doesn't mean they are right! - but often, there is no one *right* answer, but several!).
So feel free to question! And if I can, I'll back up what I say! If not, well, I'll either try or change my mind!

Learn something new!
Ok thanks. I just don't know where to draw the line sometimes and I tend to magnify potential issues in my head. So preening = OK, Good even! Over preening = BAD
I just don't know how to tell if its turned into over preening I guess :0
That's correct, BoomBoom! FDB (Feather Destructive Behavior) comes in many forms... from barbering feathers (snipping off the ends - feather at end will be an inverted "V" shape), plucking feathers (fluffy feather down instead of the colorful body feathers, bare skin [not to be confused with areas that are normally featherless], sparse feathers, etc), over-preening (allopreening a mate), to mutilation even (causing self harm, bleeding, holes, etc).
Some species, predominantly alexandrines, indian ringnecks and eclectus can have such a *hard* molt that there appears to be some FDB going on because they look like crap! After they are done molting, they look perfectly normal again!
Birds with FDB need to be *encouraged* to preen in a healthy manner to try and stop them from FDB behaviors. There's a lot of things one can try to stop a bird from over-preening and destroying their feathers, starting with ruling out medical problems, then try and enriching their life physically as well as mentally.
It's kind of like chewing... birds should not be discouraged from chewing on things, but they do need to be encouraged to chew on *appropriate* things - such as toys. Sometimes, it can be hard to find the 'appropriate' boundary of what's good and what's not.