for example, Iratu is number 1 at https://booru.allthefallen.moe/users/1 and should retain that forever despite retirement for legacy purposes
really anybody who ever did anything whatsoever with an account should retain their number, I'm only thinking of "done absolutly nothing" ones
for example these who also registered in March 2016
fierro400 at https://booru.allthefallen.moe/users/2
a0425692317 at https://booru.allthefallen.moe/users/3
ThePainTrain at https://booru.allthefallen.moe/users/4
user5 at https://booru.allthefallen.moe/users/5
DrStein at https://booru.allthefallen.moe/users/6
helvete95 at https://booru.allthefallen.moe/users/7
mr_purr at https://booru.allthefallen.moe/users/8
hentaipages at https://booru.allthefallen.moe/users/9
Zero in everything, an absolute waste.
of course, part of user numbers is it shows a chronological order of signup or registration, so I could see people retaining their original numbers for that reason, but maybe the "single digits" (now thinking of Bleach's Espada) could redirect to notable members (admins, mods) or be designated as new accounts for their use?