One of the things that will help copy editors who use twitter is a good list built around copy editing. I’d like to give a few suggestions for who to follow, and I also have my own list.
Local (For example, I live in Phoenix, Arizona)
General interest and information
Other copy editors and designers
Another reason to make a copy-editing list is you now have a list of people to bounce copy-editing and design questions off of. You can also send out requests to other copy editors, like I did when I chose to make a section for editing tips on this portfolio.