That was me! No "guy" here--I'm Patrick. Hello there.
About your argument that you can wear the same sweater for ten years and undergo many internal changes. You know, if I twist your true intent some, I kind of believe you. Sometimes we might need for something to be sort of unchanging, stable, dependable, before we make the leap to some other more appropriate "place." Saying this, I know you're saying that internal changes can readily occur, independent of our external surroundings.
But yes, I do think we identify ourselves through our objects. Objects are powerful stuff, they can move us closer to where we need to go -- they can co-operate, synergize, with the kind of internal growth you rightly flag as important. Of particular objects, I am now thinking of pcs and of how I truly hope Apple's efforts to switch PC users aren't thwarted by the recession's efforts to switch us all off. People come to associate with smiley apples and not downer pcs, and they will begin to know and eventually prefer a more people-friendly, liberal world. Buying into the better can do much for internal stimulation and self-growth.
Link: Case against thrift