SAN FRANCISCO — A year ago this month, Elon Musk turned to his favorite social media site with a question. Saturday morning, Musk tweeted that he’d deleted his list of blocked accounts on Twitter. Days later, Twitter users widely reported a new problem: They could no longer reply to tweets in their timelines using a web browser. Under Musk, Twitter expanded its overall emphasis on recommendations and added a twist. Even so, some worry that Musk — who admitted to sleeping on a library couch at Twitter — has once again overextended himself.