Twitter has made people better at English

Twitter has made people better at English for two reasons:
1. Because people are limited to 280 characters per tweet, they are forced to be economical with words. Most especially when Twitter had a 140 character tweet limit, and you could not do multiple linked tweets like you can do today. Because of this word limits, people are forced to be creative and have their idea expressed in just 2 or 3 sentences.

2. Because of 'likes', 'retweets', and 'comments', people have the incentive to say something of value. Something that will make the reader want to spread what they've read to others.

So, Twitter has made people more creative with words in both length and value, and in my opinion, has made people better with English.