Against these facts I find these two problems with OSM as it is...
1) This pond https://www.openstreetmap.org/way/1084463712 should maybe be named "LEIKKIPUISTO SANNAN lasten kahluuallas" if it even needs a name? Personally I would probably leave it unnamed. Everything on a map doesn't have to be named.
2) This playground https://www.openstreetmap.org/way/1084463715 should maybe be named "LEIKKIPAIKKA Sannanpuisto" to emphasize that it's in fact the name of the playground and not the park. Besides there seems to be two playground polygons here on top of each other. The other has a name and the other doesn't. These should be combined.

Beside these corrections I also believe that some explanations in the description tags of these objects would also come in handy to document and clarify the situation to others.