CTRL+F "delete"

Individual opinions may change over time, but if expressed publicly in a community settings, they become a part of history of that community and its discussions. I think disassociating usernames from comments without purging the comments hits the right balance. Different people and communities may choose otherwise.

On that note, I wish websites, in particular and especially HN, were a bit more up-front about this. Here, the information about moderators' approach to account deletion is somewhat buried - it's at the bottom of FAQ, and important clarifications are another link away. In general, I wish all community-hosting websites put information like this front-and-center during registration, not buried in an inscrutable ToS, so that users could make an informed choice before joining (or at least as much of an informed choice as you can make, if the choice will be binding a decade later).