>> I knew I was the only poor person at my tech startup because people kept bragging their bodily purity based on what they would not eat or drink, and I could only feel pity for them.
YM without an "about" or similar? Not very common IME, but seeing it now is probably a harbinger of more to come. Feels congruent with "because [something]" (without an "of" in between).
Is it common to use "bragging" in this way?