Credit-card super users are searching for answers amid a string of shutdowns from Chase, as billions

Members of online communities of credit-card super users have been freaking out over the past year after hearing stories from some JPMorgan Chase cardholders that the bank shut down their credit-card accounts. Since the credit-card rewards arms race ramped up a couple of years ago following the Chase Sapphire Reserve launch, credit-card enthusiasts who make a hobby of accumulating points for free travel and other perks have swelled in numbers. Like card sharks in a casino, these customers...