There are two labels because there is a multipolygon for the Red Sea which already exists for a long time and has many name translations, and recently someone add a node with place=sea for the Red Sea. https://www.openstreetmap.org/node/11511151629/#map=16/20.33252/38.32328

Is this potentially a data issue we should fix in OSM and not something we should fix in the tiling?

I think so. I asked in the changeset which @zstadler made if it would make sense to move that label to the relation

@wipfli, I have not created this node or the relation. That changeset is just about moving the node from an incorrect location.

Please feel free to add it to the appropriate relation.

Thanks for your fast response @zstadler

If I add the node to the relation and leave the place=sea and name=The Red Sea, I think it will still show up as a separate thing on our map, right @bdon ?

I think that in general many OSM place elements are mapped twice: as an area and as a node. This is well captured in the OSM wiki.

IMHO, labels for places should be based only on node places.