What I'd actually like to see is a system where you get to rate each card in terms of how much you enjoy playing with it, and then the average of your and your opponent's ratings determines how likely each card is to show up. Obviously that would take more work to set up.
This is how I think the ban list should work, but without a rating, just a Yes/No. You "ban" some cards, and your opponent "bans" some cards. If both of you have a certain card "banned", you won't play with it. It's not a real ban, but if you and your opponent mutually agree that you would like nothing more than to never see Rebuild, it won't show up, and you'll both have more fun.
But if someone wants to play with a rotation of all the cards, including the most hated ones, they would still get to do that, even at high rankings where maybe a lot of players have Rebuild or Possession or whatever "banned".
The problems with a ban system where one player banning the cards means they absolutely won't show up ever, in auto-matched games, are:
1) Some players may want to play with a selection of all the cards, and don't really have this as a choice if banning cards is popular
2) You could, potentially, game the overall rating system slightly by banning your personal lowest win % cards
Maybe the effects of both of these are very minor. But requiring both players to have "banned" the card to prevent it from showing up would solve these problems. On the flip side, the banning might not do much at all in this case, if hardly anyone uses the feature...
As a compromise, what might work is what Jimmmmm suggested, but only with ratings of 100% and 0% (could still just be implemented as a 5 card ban list). If one player "bans" the card, the chance of it appearing is halved relative to the normal probability of it appearing. If both players ban it, it will never show up. Might be a reasonable compromise, since still any card *could* show up (vs. players who may prefer to see that card), and you would still see your least favorite cards less often.
I flat out disagree. If the feature is to be implemented, I will ban Possession because I hate the card and find it unfun. That means I never want to see it again. With your suggestion, I would then have to restrict myself to playing others who also ban it, which restricts my pool of available players and lengthens wait times.
If we are going to go that route, then why have a ban list?
Sorry, I don't understand the bolded in your quote. How would you restrict yourself to playing others who also ban it in auto-matched rated games? You would just see Possession sometimes. Strictly less often than you do now, though. My suggestion didn't have anything to do with lengthening wait times or allowing you to pick opponents based on your card preferences. (Maybe I worded something poorly?) Cards on your ban list you would see half as often as you do now; assuming your opponent doesn't have it on theirs. Cards on both players' ban lists would never appear.
I guess the overall philosophical question is what should rated games be about. If you have a unilateral ban list, for any particular game, it doesn't matter what cards were banned, because they're just not in the kingdom, and it's just like the randomizer didn't pick them. It only really matters at a more macro level, after tens or hundreds of games. If you really wanted to climb the ladder, you'd probably ban the swingiest cards earlier in your climb, then perhaps switch to the cards you're not as good with at the top (or keep banning the swingy cards). Would the effect be large enough to matter and is this a concern to current top ranked players?
Another possibility is just making the most hated card(s) banned by default for all players for rated games. If so many players hate Possession, then it can join Stash as a banned card at least for rated games. That gets around the system gaming issue. I'm not really advocating for this, but it's a way to do it.
Banning the intersection of a list of disliked cards that is allowed to be any length shouldn't offend anyone,
It lets you hugely game the system, and for sure some people would not like it and rightfully so. I personally would not like it. I don't want to have to ban all the fun swingy cards to be competitive with other people who do so.
You have not changed my opinion. I don't like your idea and still like mine.
Can you expound on how banning the intersection of a list of disliked cards would allow you to hugely game the system? It means that if both players have banned a card, it won't appear. Otherwise, it still could. So if one player bans Swindler, Cultist, Rebuild and Possession, and you only ban Possession, then Possession will not appear in this game. The other cards still could. If one player bans no cards, all the cards could appear. I don't see how this is gameable, but the ban list in this case also probably doesn't do anything most of the time...
This would be more like those Rebuild "gentleman's agreements" where both players decided in chat they would skip Rebuild. Except, now it gets auto-replaced with a different card if these preferences are expressed in the system before the games start.
ETA: We actually already have this "intersection ban" system, in a sense. These are the subscription levels. If you're not subscribed to cards, they are soft banned. If both players are not subscribed to a card, it will never appear. I mean, you can't game it really, just pointing out that this is not really a radical departure from how rated games work currently. (i.e. not all rated games pull from ALL cards as it is.)