No spam filter (there is one, allegedly, but it’s invisible, non-configurable (!), and missing obvious spam words)
(there are comments on the official forums from 3 years ago saying “we need some basic anti-spam tools” and the author replying with “we’re working on it”)
No spam controls for reactive processing (banning users, marking comments as spam, etc).
Each comment can ONLY be deleted one, by one, by one, requiring 6 mouse clicks per deletion!
The concept of a list of comments, and a checkbox next to each, and a “delete selected comments” is now well over 10 years old – and it only takes a few minutes to implement with PHP + SQL. If you ever find yourself making a web app for general usage, please don’t forget this core feature :).
(I’ve been too busy for the past month making actual iPhone apps to finish my free PHP FAQ platform, but watch this space, shouldn’t be too long now…)