People, please.
If you are replying to more than one person and addressing them all, then you keep all the names upfront.
If you are addressing one, and keeping the rest in the conversation, then add your reply between the names
"@a @B @c you an arsehole" is saying they are all arseholes
"@a you an asshat @B, @c" tells a they are an asshat and c that a is an asshat.
Gotit?