Yesterday I decided to see how many tags I could cram into one post. Today, the experiment has concluded. We now know how many tags you can have in a single post. That number is 2177. Yes that's correct, you can have a post with two-thousand-one-hundred-seventy-seven tags if you so desire. Happy tagging!
You can view the results in all their glory here (fair warning, it may be super laggy on your computer and it will more than likely crash your phone). I was a bit disappointed that it didn't cause Kinja to explode in glorious fashion. Once at a certain point it just said it couldn't save the post. It still is an interesting, albeit useless, tidbit of information to learn though.