According to this:
Summoner's Code IV: Enjoy Yourself, but not at Anyone Else’s Expense
“Short is the joy that guilty pleasure brings.” -Euripides
Making games is our business, so it should come as no surprise that we want you to have a lot of fun. We want you to get excited, to have tension-filled moments, and to celebrate your success. This doesn’t mean that we’re okay with you ruining anybody else’s day.
Remember, taking a jab at your friend in the middle of the game is a lot different than making a glib remark at a complete stranger. Someone who is unfamiliar with what you consider playful may take your comment as an attack and react unfavorably. If two players on a team start fighting, good communication and teamwork become nearly impossible. Once communication breaks down, the likelihood of victory is drastically diminished. It isn’t uncommon for simple, good natured teasing to spiral out of control into a loss, so do yourself a favor and don’t run the risk of sabotaging your own success.
The banned player continued the spam because it satisfies his troll nature and is pleasured by the fact that people are annoyed by it.
This is another one of those trolls trying to find loopholes in the Summoner's Code.
Glad to see tribunal working as intended.