ananymous chat was disabled because the vast majority of the time it was used for verbal/textual abuse. requiring login for chat allows the lichess team to remove access from confirmed trolls/potty mouths.
I did have some good conversations with other anons, but eventually turned off chat altogether because of the people who would wait until they were winning and then verbally berate their opponents. many times this happened, I would miraculously turn the game around (a few times I was winning when the trash talking started) and the player would ragequit if they saw the m8 coming. well after the ragequit sometimes that time control would be near impossible to play because (assuming its the same anon) some anon would park and wait for a game with that time control and then join and abort, or join and wait for me to move and then abort.
tl;dr, anonymous chat is prone to abuse.
I did have some good conversations with other anons, but eventually turned off chat altogether because of the people who would wait until they were winning and then verbally berate their opponents. many times this happened, I would miraculously turn the game around (a few times I was winning when the trash talking started) and the player would ragequit if they saw the m8 coming. well after the ragequit sometimes that time control would be near impossible to play because (assuming its the same anon) some anon would park and wait for a game with that time control and then join and abort, or join and wait for me to move and then abort.
tl;dr, anonymous chat is prone to abuse.