While there are some clothing choices that could be sincere, what I meant is that I don't understand what those clothes sincerely are. I thought skinny jeans were a recurring fad, and the big glasses were fashionable or meant to get attention or something.
For your other questions, I think someone who spent 2 grand on a suit just to be showy is pretentious. If they did it because they really like expensive clothes, that's better (although probably still vain). If they did it because their family comes from money and they're just used to wearing crazy expensive stuff, that would be the most "sincere" way I can think of.
I don't understand your definitions of sincerity, pretentious or vain. I attempted to, by asking you a sequence of questions. They only confuse me further. My only intuition is that you think _vain_, _sincere_ or _pretentious_ are absolute. I think they are relative. E.g. you spending time not working in a cotton field 20 hours of a day to feed your family might be seen as the vain games of the rich by a farmer in third world.
I went back and re-read the paragraph. My understanding of it was that the author opined that things like artisan foods were a sincere expression, an output from a human being who believed truly that this was something that they were doing for themselves as opposed to say doing it to appear "cool". Now, I don't personally claim to have any special intuition of those who make artisan foods considering I have never interacted with and figured out why people do such things. I presume they like the rest of humanity have a wide range of reasons.
For your other questions, I think someone who spent 2 grand on a suit just to be showy is pretentious. If they did it because they really like expensive clothes, that's better (although probably still vain). If they did it because their family comes from money and they're just used to wearing crazy expensive stuff, that would be the most "sincere" way I can think of.
When General Alexander wore jeans and a t-shirt to last year's Def Con, it looked pretentious. http://blogs-images.forbes.com/andygreenberg/files/2012/07/S... It looked like he was wearing a costume and imitating someone else hoping they would think he was like them. He looks like he would feel better in a uniform, like the one he wore to this year's Black Hat. http://gigaom2.files.wordpress.com/2013/07/alexander2.jpg