It's not because of an out-of-date browser. I was on school WiFi the other day, using this same version of Google Chrome on my mac, and I still couldn't type anything. You can ask Creator of Chaos for evidence. Not sure how to fix it but I got off the school WiFi and went onto my home WiFi and it seemed to do the trick. Might be because you're using a restricted network or have a slow internet connection. Not really sure.
That's not it either. My phone is connected to the same Wifi and it lets me post just fine.