How often is too often?

Got the "you are submitting too often" message today, making my third post in 36 minutes. I like to read HN and then move on with my day. Most days I have nothing useful to contribute. When there's an issue that I can contribue to, I like to.

What is the problem here? Is it the huge response trees? One thing that frustrates is that if there are two good "root" posts, the second will be lost under all the replies to the first. Indeed responding to the best first post is more likely to be read (i.e useful) than making the point under the main article.

Come on. Fixing stuff like this with lisp is easy, right?