About [[Osm:Activerecord.models.old node tag/en]]
I cannot find where this text is used and how to translate it. Does "Old Node Tag" mean "node tag which is old" or "tag of the old node"?
It's quite possible that it's never actually used - those are generic messages that rails creates for each model that would be used as part of things like any rails generated error messages relating to the model.
The main time that they get displayed to the user is in validation errors, but validation errors shouldn't really be possible on the history models and even if they did happen I doubt they would ever make it back to the user.