Hats, tons of stuff in the fraud combating trade restrictions, people not happy with gift wrap, renewed bitching about the 3 month chest trade restrictions people not happy about the drop system. I get why people are upset, but it all drowns out real conversation, and a large part of it is driven by people upset it hampers their ability to profit off the system, and the comments come off as just people who want every thing for nothing or feel that they paid $10 so valve should cater to them.
I'm not taking a stance with the redditors here but personally I had spent hundreds of dollars on Dota hats during my first year of playing but lately, since probably TI4, I've completely gotten over it. The trade restrictions do not help but personally I got sick of stuff like rare sets/items in chests. I was never trying to profit off the system. I spent my money gladly, but it has gotten a lot harder to frivolously throw a few dollars here and there to get something that I want. Instead you have to drop large amounts of money playing Valve's lotto games.