The OK trends blog to me cannot be read as serious social statistics analysis. It's intent is to get hits and keep their sky high google page rank. It is almost entirely a marketing ploy, and I find it impossible to source them on topics like "what makes a good picture?", "what makes a good message?", "are you all a bunch of racists?", &c.

One of the reasons that instrumental rationality is hard is that acquiring good data is hard. Imperfect data is generally better than no data however and there are other sources where you can find research into some of the same questions that OkCupid covers. Most of the advice in their 'Don't Be Ugly By Accident' post is just standard stuff for portrait photography for example which any book on photography would cover in great detail.