On cleaning up comment module

now, go tell me which elements are present in the old comment form and which are present in the new
here is a hint. in the new, everything is always there, it's consistent and easy. in the old, answering this question probably needs a whiteboard and a flowchart
[...]
meeting with comment_render for the first time is a memorable experience
not much different from meeting headfirst with a brick wall
[...]
it's worth mentioning that before 5.0 this cleanup was not really feasible
it's like Drupal 4.7 was a nightmare, Drupal 5.0 is the promise of a new day and Drupal 6.0 is the shining new day

— chx to dmitrig01 in irc