Chat abuse that needs to be fixed: And it isn't verbal abuse at all.
Players can create false messages in chat, and may either use them just as a silly and harmless joke, or even as a way to trick other players into leaving the match for fear of a punishment from Riot. I'm going to explain below what it is I'm talking about;
If your message is long enough, it takes up more than one line in the chat box. If the first line has enough characters in it, you can make the second like look like a different message by making it a typical system message (a surrender vote for example) or adding a fake time stamp to it. If your initial message is short, you can just put a bunch of spaces after it to take up the space and push the next part to a new line as I do in the picture below (was in an empty custom match);
Some have been using this to trick other players. While it is easily spotted, if you don't know about it you may be easily duped into, for example, burning all your CD's and spells and suiciding when you think the enemy just surrendered, or logging out and changing your password because you think there's a security issue that could get you banned.
This should be fixed. My suggestion is that new lines for a long comment have a special character in front of the line to show it is part of a continuous message, and to limit spaces to one (so putting 15 spaces to reach the proper character number will only result in 1 space and the next trick message won't get pushed to a new line).
Until then, you all need to report people who abuse this by trying to trick people. Saying "[4:20] Snoop Dog has entered the game" is pretty harmless, but that's not all it's being used for.