That's not covered in this article. And it seems crazy to me that they would vote to shadowban you without attempting to talk to you at least a little. Is that what happened? If so, that's nuts.
A week or so ago, it was pointed out to me that ircmaxell was also banned from reddit - I think it was a shadowban as well, since his username still appears as the submitter on some items, rather than "[deleted]" - because he was submitting too many links to his own blog.
Now, this isn't just some average blogger. Anthony is a very well known PHP developer - by which I mean he develops PHP, not just in PHP, and has voting rights regarding the direction the language takes. (Please don't hold that against him, Jeff.)
While I'm sure he was posting a lot of submissions for his own site, it was really great stuff. The first I really heard of him was due to a series of articles he and another developer wrote as a guide to understanding the internals of PHP with directions on what various C code was and how it hung together. It wasn't spam, at least not by any definition I care to recognize.
This didn't matter. Quality didn't matter. Apparently, one of the moderators to /r/php even went to bat for him with the admins, asking that the ban be lifted. The admins didn't care.
Meanwhile, many people submit a lot of content they also made themselves - memes. If you want to make a bunch of advice animal image macros and upload them to imgur, that's fine. If you write a five part dive into the guts of PHP's internals, you're banned.
It's funny too, because maybe I'm remembering incorrectly since it's been so long, but I seem to recall early reddit specifically saying that it was cool to submit your own stuff, and even encouraging it. Now, there's some sort ratio of yours-to-others content that you need to keep in balance, otherwise you're marked a spammer, regardless of how good your own content happens to be.
The fun of closed walls.