There are many Twitters now, but we may never have another Twitter again. As the eminent Twitter of its time, Twitter served up a lively, often incoherent mix of paradigm-shifting cultural phenomena (Arab Spring, the Me Too movement, Black Twitter), breaking news, corporate existentialist brand building, tweet-addled U.S. presidents and hardcore porn. Now, we’ve got options — maybe too many at this point — and Meta’s newly launched Twitter clone Threads just opened its doors. People are flooding in, mostly thanks to Meta’s shrewd decision to whisk people over to Threads straight from Instagram. Getting started on Threads is a...