The origin came from "cultured runner", refer to pelari veteran atau yang sudah lama ada di scene running. "Kalcer" is how we pronounced "cultured".

Usually, "cultured runner" became the reference for newbies, on how he/she run, looks, his/her weapon of choice (gear, shoes, etc).

The obvious one is, of course, about outfit (head to toe). Newbies can instantly catch up with "cultured runner" through copying outfit, most likely high end products that become synonymous with "cultured gear/outfit".

The joke among us, when someone wearing high end products, there will be instant comment: "Wah, udah 'kalcer' nih!" (Wow, you're cultured already).

The shortcut practice of being "cultured" through outfit triggering those comments you mentioned. It become a mockery, derogatory remarks, although at first, it is a compliment.