Okay. It's been a while since I log in into my Smogon account. I've been busy lately. Since there's a Chatter suspect and I meet the reqs, I see why not? Here are my thoughts.
What makes a metagame popular? Because it is fun? Because it is balanced? Yes, all of them are correct, however, what attracts people to play a metagame is they are desirable. Of course, every people has their own definition of what's a good metagame and not, so "desirable" is something subjective. However, from what I've observed so far, there are three main points that makes a metagame desirable.
1. Fun. Probably the most important point. Inheritance is a metagame with lots of room for creativity. Every pokemon has like 2-3 viable sets. This is probably one of the main reasons why Inheritance is a fun metagame because you can always discover new ideas. Chatter is one of the moves that makes the metagame "no fun" because it annoys people. This is also why people cries about Whimsicott in No Guard Galaxy, Prankster Sleep + Subseed isn't broken, but it's SOOO annoying that people want it banned.
2. Competitive. An important point that is linked to point #1. Luck is a part of the metagame, but do people like it when you win because of crits or confusion hax? This is why swagger is banned. Competitiveness is also part of the fun and luck takes it away. I believe Chatter fulfills this category. Not only it has few counters, the fact that you can buy free turns because of LUCK is what makes it uncompetitive. And one turn is very important because in that turn, Chatot inheritirs can set up to break you Special Wall or something.
3. Balance. The least important aspect I think, but still important, because it's pointless if a metagame is balanced but not enjoyable. It won't attract people. However, if there's one element that is too good so that everyone are forced use it to the point that it takes away the FUN of the metagame (point number one), it must be removed. Unbalanced elements are what people call "broken." In this case, Chatter doesn't break the metagame.
In this case, even though Chatter doesn't break the metagame, it is unfun and uncompetitive (in my view at least). For this reason I'm voting ban.
On topic about Hoopa C, I don't believe it to be broken. Of course you can't counter every Hoopa set, it applies to every pokemon here, but there's specific counters for each sets (except maybe Protean, but it's Protean). The Adaptability Porygon-Z set is walled by most Dark types, while the Super Luck set people are talking about is walled by Meloetta (Togekiss doesn't get Dark Pulse). Non Psyshock variants are walled either by Goodra or Florges. It's also slow, easily killable because having 2 4x weakness and bad Physical Defense. There are reasons why Hoopa is ranked B+ in Viability rankings, not even A.
