Good: I got support from people when things in my DnD group got weird.
Bad: Once, I asked a technical question that I had asked people irl and researched a lot and not found what I was looking for. On reddit, I had people making assumptions and nitpicking the terminology while avoiding the actual question completely. It was a good example of the CS/math departments friction (which makes a whole lot more sense to me now). I did get a better answer on another site by just posting the equation and using zero jargon but I ended up abandoning that topic bc it was impractical.