At some risk of stepping into a controversy I have nothing to do with... Aaron was not an original co-founder, and when his company merged into Reddit (with a "co-founder" title as per agreement) every indication is that that arrangement didn't work out for anyone. So I don't blame Reddit for not including Aaron in the company history, as it wasn't his idea, he didn't start it nor grow it, and his presence apparently never "clicked" with the others.