Twitterwriter 

A person who writes regularly on Twitter.

I am a Twitterwriter.

Twitterwriter by thecommentator October 20, 2009

Twitterliterate 

Being well-versed in the new language, slang and hashtags commonly used in the social media world of Twitter.

"Finally, I have mastered how to properly tweet! I am now fully Twitterliterate!" exclaimed Toks, joyfully.

Twitterliterate by homopinionation April 21, 2013