I guess it makes sense to just brand them with the scammer tag so it's evident, but who says they don't already have separate accounts to scam others already? Not every scammer is a genius, and might not be able to figure out a way to connect again if their IP was banned. Just saying.
It's called using your brain and investigating people's habits. A example is me, I like to end or begin a post with four dashes most of the time.
A lot of people don't capitalize 'i'
Some people don't end with punctuation.
Most of the time people have habits, and you could most likely draw something from that. If they're a huge scam artist, and have been planning their scam for months, we just have to be cautious, eh?