It's Not a Bug, It's a Feature.
Added 2018-10-24 23:40:27 +0000 UTCSo in TF Card Battle .22, I accidentally uploaded a development version that was testing not discarding cards at the end of the turn, but rather being able to hold cards you didn't want to play.
I was intending to test this and see how it affected the game. Well, I guess all of you are doing the testing now. I'm going to patch it out, but as long as it's out there, tell me what you think.