There's been a large misunderstanding
I keep seeing people throughout the boards say that Riot is fine with trash talking, as long as you aren't a dick to your teammate. However, this is a very misinformed statement. Why is that? Well, let's look at the actual definition of "trash talk."
Results according to dictionary definition
Trash talk - insulting or boastful speech intended to demoralize, intimidate, or humiliate someone, especially an opponent in an athletic contest
See that guys? Insulting speech. Demoralize, intimidate, humiliate.
Banter - the playful and friendly exchange of teasing remarks
As you can see, the two are polar opposites. So, to say that Riot will not ban you for trash talk is simply not true. They ban players daily, loyal or not, for this exact reason. A large number of people on the boards seem to be confusing trash talk with banter.
Being a logophile myself, it was irritating for me to see people misunderstanding two completely different terms. Just wanted to clear things up. Have a great day guys!~