I understand the sentiment, but if we're trying to overcome our biases/be less wrong, perhaps this is exactly the sort of practice we need?

Maybe, but it doesn't take a lot of effort to find political opinion (it takes more effort to avoid being exposed to it!).

On the other hand, talking too much about politics on Less Wrong is a serious risk for the community. I don't want this to be a place where people can come comfortable in the opinion that most people will share your political views, where people congratulate each other for how rational they are for having the same opinions. So the less signaling about political affiliation of members, the better.