>>18876
The .@ only makes sense if your tweet starts with @. Actually, you need to put anything in front of @ so your message doesn't get classified by Twitter as a directed message.

This is good:
".@CNN Hello"
This is good too:
"Hello @CNN"
This is bad:
"@CNN Hello"
This is good but nonsense:
".@CNN .@User51 Hello"

Read more if you are interested:
https://www.themuse.com/advice/mystery-dot-the-best-kept-secret-on-twitter