Foothold was obvious enough for me to miss it for way too long 
For user1 to user2, when I landed in the home directory, I saw a .viminfo file, and the thing everyone’s looking for was in it. Thankfully for me, for some reason it didn’t work so I kept working and finally got it the regular way.
But, for everyone, please, please, clean up the place before leaving, it can really ruin the fun for the others !
Anyway, good box, even though the user switch drove me insane 