tweet: Millennials use "lol" like STOP at the end of a telegram lol
tumblr response: REGRET TO INFORM YOU YOUR SON HAS DIED FROM TRENCH FOOT LOL HE SERVED WITH COURAGE AND HONOR LOL PLEASE ACCEPT OUR DEEPEST CONDOLENCES LOL
It's a piece of punctuation that signals the precedeing text was meant to be lighthearted and to please not take it too seriously. Which is very much needed as on the internet sometimes people take things very seriously.