I didn't know that the Codex will be populated by "First mapped by" tags though. Well, it makes sense, but is unfortunate. Personally, in my opinion adding a "first mapped by" tag was a mistake, but Frontier have said that it's deliberately so that new players can get to tag stuff again, even within the bubble. Meaning it wasn't an unintended mistake, it's by design.
The "first mapped" tags will only apply to stellar objects mapped using the new probes as far as I am aware, this is a new category, the old tagged names will still be present so this will in no way replace those, so first tagged will still exist, people who used their DSS on planets and moons will still have their name on the bodies, but the "first mapped" bodies with locations will be added. It's maybe not ideal, but it was always going to happen considering that ED is very much a game in development. And just imagine when atmospheric bodies finally get added, we will have a whole new raft of things to put our names to. Someone did suggest we should also have a "first landed" tag as well as a "first mapped" and that's not as silly as it sounds at first, I mean who doesn't want their name listed as the first person to land on the "planet of death" or the landable body with the highest gravity ever found.
If this was a game developed following traditional processes we would all be let free into a pristine galaxy with the opportunity to put our names on lots of different things in many ways, but then we would still be waiting for it to come out of alpha like another game that I shan't mention here!
Because they chose to release it this way there are always going to be issues like this, it's inevitable and getting upset about it isn't going to stop them now or in the future when similar issues crop up.