Unfortunately, the node is not added automatically. I believe the purpose is to interconnect the sidewalk and road networks in order to make them routable. If the sidewalk does not share a node with a road then routing software can't give you directions accurately.

"Marked" mean that there are markings painted on the road, but there are no traffic signals. You can find more info on osm wiki: https://wiki.openstreetmap.org/wiki/Key:crossing
Cheers