The Belfast man announced his exit to his 15,200 followers around an hour before his account disappeared on Monday November 20.
Lawn – along with Adam Patterson and Fran Harris – wrote Blue Lights, a BBC drama following three probationary PSNI officers which premiered earlier this year to great success.
A second series of the show – starring Sian Brooke and Katherine Devlin – has been commissioned, with filming beginning in 2023.
He also wrote three-part series The Salisbury Poisonings, which depicted the story of the 2018 Novichok poisoning crisis in the English city, as well as 2022 crime thriller Rogue Agent.
In his final post on the platform, formerly known as Twitter, Lawn said it initially had a positive impact.
“My final post on Twitter/X,” he began.
“On balance I think it made the world better for a decent while, and then in a very short time managed to make it significantly worse in all sorts of different ways.
“Goodnight, and good luck.”
Current X owner Elon Musk completed his acquisition of the company in October 2022, after which he introduced a series of reforms and management changes, reinstated a number of previously banned accounts and reduced the workforce substantially.
Musk introduced paid verification checkmarks in November 2022 and acted as CEO of the company until June 2023, when current CEO Linda Yaccarino took over.
Twitter was rebranded to X in July 2023.
It comes after NI-born actor Sam Neill also left the platform earlier this year.
The 75-year-old Jurassic Park actor announced the news by posting a video of himself waving goodbye to his followers.
In a brief farewell message, Neill said he would still be active on Meta platform Instagram.
“My friends, I’m just going to walk quietly away from Twitter for now,” he said.
“I am not happy with what’s happened at Twitter and I’m not happy to be in a place that is so angry and divisive.
“But I’ll still be alive on Instagram. And I miss my blue tick!”