I would like to improve the comment editing for user by adding a simple WYSIWYG editor, and I selected CLEditor as possible good candidate because it is light, customizable and jQuery based.
I searched if it already exists a plugin that implement it but I was not able to found any. So I decided to write my own plugin.
Do you have any suggestions about which WordPress actions or filters should I look to start?
In modern WP all of comment form is produced by extensively hook-able
comment_form()function. Also see WordPress Theme Tip: The Comment Form tutorial.Other than that you will likely need to enqueue scripts.