I can confirm the issue: also I see nodes on the waterway which are NOT part of the way. I find them on many waterways in Laos. I checked one of those nodes http://www.openstreetmap.org/node/1550235958 and found out that the changeset was created many years ago in an old version of JOSM - by the same user as your example.
Actually, such nodes should be easily found:
- download the data in JOSM
- select all
- run the validator
These nodes should show up under validation warnings.