If you use some sort of an admin system they may use these datastores. If not, I’m not even sure if Roblox systems check if the player has DataStore data on that game or not, I’d say very likely, systems don’t check that. Before datastores v2 update, it wasn’t even possible to attach user ids to datas.
I haven’t seen anyone getting banned for this but you should not ignore them. I can’t talk about the legality much but afaik, companies have to comply to right of erasure laws in most countries so logically devs are also required to comply, however I’m not sure if this requirement is legally. I’m not a lawyer.
No but Roblox has shared some guides on automating those.
For future features I strongly recommend using datastore tags, especially the UserId in case that Roblox starts to automate those.