No captcha?

Hello,
I am learning programming and just discovered this website. But I am curious, how does it protect its users from spammers (people who post illegal or annoying things) without a reCaptcha? I thought clicking this blue box is required to prove that you are not a robot, can you please share any javascript that you use for this purpose?
Thank you and have a nice day,
Brian

That reminds me of when I had a 20-strong botnet at the university. I would write projects for other students for cash or booze, and I would hide a backdoor in the executables (because most of them were too lazy an/or retarded to compile the code themselves and wanted an exe too). I used that to spam the old <marquee>/prague/</marque> with randomly generated sentences. Those were the times.