What about Product Hunt for finding a co-founder?

I do not think founders looking for one another is the best way to find co-founders. I meet a lot of people from different channels and when someone has similar thesis as I do regarding business, I simply talk more. Recently I met someone on Reddit who was sharing their own videos explaining complicated database/machine learning related topics in plain English. Their style resonated with me since my mission is to build products that are really for non-technical people, no engineering needed. So I reached out and now we share updates with each other and seeing how this goes. When we are busy being founders or creators - we are busy doing that - that is what you should search for - the telltale signs of a founder who is similar in your thought process. A search box on any site will not get you there - talking, working together on projects will.

Given you can make amazing encounters pretty much everywhere, I don't see why one wouldn't be able to find a co-founder on PH. I would though think it's just a mere intro. Being co-founders is much more than a simple "association". We all know creating startups is an eventful ride, full of ups and downs. The founding team is the cornerstone of the journey and needs to be rock-solid, capable of genuine discussions, of disagreeing without any grudge being held, of moving past tough times - among others. This requires more in-depth relationship than just "online dating", no matter which platform is the source of the introduction. Potential co-founders that found each others online should indeed work together for a while, learn to know each others and see if they can engage in a dispassionate, long-term relationship.