'Concerning': Mark Zuckerberg trolls Elon Musk on Threads with one-word responses, just like the Twitter owner

• Mark Zuckerberg, the CEO of Meta, appeared to poke fun at Elon Musk for the second time this week.
• He responded to Threads posts with one word — "concerning" — in the same way Musk often tweets.

Mark Zuckerberg appeared to take another jab at Elon Musk on Threads, his new Twitter competitor.

The Meta CEO responded to two posts on the site by simply commenting "concerning," along with a crying laughing emoji, appearing to reference the way Musk often tweets.

The Twitter owner has responded to tweets with the word "concerning" at least 26 times, Insider found after reviewing his past replies.

Zuckerberg first replied with that reaction when the social-network entrepreneur Nikita Bier joked about a user leaving the platform and then again when a Meta engineer said that Threads appeared to be censored from Twitter's Trending feature.

Philip Fung said in a Threads post: "Unlikely this is not in the top 30 US trends for the last day. Makes sense, but also shows how hard it is to stick to your principles when it is against your interests."

Soon after Meta launched its latest social-media app on Wednesday, lawyers for Musk sent the company a cease-and-desist letter, claiming that it was a "copycat" platform.

The billionaire criticized it Saturday in a tweet: "Threads is just Instagram minus pics, which makes no sense, given that thirst pics are the main reason people use that app. How many times have you read comments on Insta pics & wished there were more? Personally, never."

A few hours after Threads rolled out, Zuckerberg appeared to mock Musk when he tweeted for the first time in a decade and posted a Spider-Man meme.

Meta and Twitter didn't respond to requests for comment from Insider, made outside normal working hours.