I see it frequently on F.R., it means the poster is about to attribute something to you that you never said nor even implied.
People will infer what they will, no matter if it's true or not.
Use of “So...” on FR:
Not so bad here IMHO. I see it as a verbal tic, like ‘ya know’ or a teenager’s ‘like’, but used when the speaker wants to say “listen up, I’m about to say something important” - and with almost every sentence and totlally superfluous. Here, the people in the story were tweeting it!
“Is the use of the word “so” to begin sentences not a feature of your dialect?”
It is, and wish it wasn’t. Maybe it’s localized. Interesting.