Who decide what is rendered by Mapnik on the main map?

I have a few recommendations to change the rendering rules for the Mapnik Layer in The Map. I found out that the rules are in the osm.xml on trac.openstreetmap.org. Can anyone change this file or only a few chosen one? Is there any discussion forum on that or only the separate trac entries?
To be specific the biggest problem is that in Hungary the name of every village apperars three times on the map, because the admin_level=8 boundaries were uploaded for the whole country. So a village name get printed on the map once for landuse=residential, once for the boundary relation and once for the admin_centre in the boundary relation. We don’t need to show the latter two. You can see an example here:

http://www.openstreetmap.org/?lat=47.47547&lon=17.37374&zoom=16&layers=M

Ugly, huh?

Other things I miss from the main layer are tower:type=observation, leisure=water_park and leisure=beach_resort.

One thing I see is that the tagging convention does not match what is generally done, that is why the results are not rendered as expected.

Named landuse tags are rare, and should not be used in this case. Villages and small towns will often have more than one landuse, and it would not make sense to name them and have every one show up on the map as the name of the village / town. A good example of a named landuse might be a shopping center: landuse=retail , name=‘Trading Square’ . It is often not feasible to use names during a mass landuse import without manually reviewing them to see which names to use. I would recommend removing names on landuse.

Similarly, the tags currently on the admin_centre node do not belong there; they should only be on the boundary admin relation. admin_center should be an untagged node as a member of the relation with role ‘admin_centre’. Later someone with local knowledge would tag that location correctly as Post Office, Court House, village_green, etc with the proper name.

I think you’re right with landuse but not with admin_centre. The admin_centre should be a node with the tag place=*. It is intended to be used by applications that can’t calculate the admin centre, because there are many such nodes within the boundaries or the node is outside the boundaries. The role ‘label’ should be used for labels.

But my main question is who allowed to change the style file and is there a discussion forum on the main style file?

Mapnik style file changes are coordinated using the OSM Trac, under the Mapnik component. http://trac.openstreetmap.org/query?component=mapnik&order=id&desc=1 .

Anyone can submit a modification as a patch to the Trac. I don’t know if there is a discussion forum on the OSM Mapnik style file.