When I see two spaces, especially in proportional text, I use it as evidence of the writer being a luddite or "past it". Only one piece of evidence, not conclusive. Probably most of its explanatory power comes from it being an indicator the user is old, educated in typing with a typewriter.
When I see one space, I tend to suspect the writer is not a (very good, anyway) programmer, and is not particularly concerned with how text looks in reader software that uses monospace fonts -- and probably learned to type on a cellphone. I also expect to see such people spell "you" with the first two letters missing at some point.