I'm in favor of using one space as two are just too much. But considering the origins of this it might make sense introducing ligatures in monospaced fonts which move the dot to the left edge when followed by whitespace. This could slightly increase the gap. Though I'm not sure if this little difference is worth it.
This sound's like tabs-vs-spaces. Either 1 or 2 should be fine, and the document itself should have a convention that's auto applied, or the viewer can choose how much horizontal space to show for a period.
In internet text, I don't know that I've noticed one way or the other, using 1 myself.
1 after comma for sure. 2 or 1 after full stop should be your choice on comment forums. I usually find it easier to read and follow material when there is spacing.
