obsissive
A person who can't stop replying to every message, even if it's just to say 'hi'. They're like a dog that won't stop barking at nothing, and they're hoping someone will give them a treat.
"I replied to your message just to say hi. That’s important."
Thread: "I’m not obsessed. I’m just making sure you know I’m here."
DM: "You didn’t say hi back? I’m insulted."