The tags which are placed later by on_chunk are visible. I placed some log() and they tell me that the code is being executed like it is supposed to be.
function add_chart_tag_for_all_forces(surface, position, text)
log("tag_all")
for i, force in pairs(game.forces) do
log("tag")
log(force.name)
log(text)
force.add_chart_tag(surface, {position = position, text = text})
end
end
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:104: tag_all
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:106: tag
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:107: player
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:108: Leocord Reef
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:106: tag
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:107: enemy
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:108: Leocord Reef
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:106: tag
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:107: neutral
9363.713 Script @__Annotorio__/prototypes/map/island_naming.lua:108: Leocord Reef