The Brief: Go off is a phrase used to egg someone on.

Bluesquiggle
DEEP DIVE

Telling someone to “go off” is usually a way to praise them and to encourage them to keep doing what they’re doing.  “Going off” can refer to talking about something or doing something. The phrase can also be used more vaguely, usually as positive reinforcement, but sometimes sarcastically or negatively. The term is attributable to African American Vernacular English (ebonics). Currently, it’s popularly used among Kpop stans.

But Go Off I Guess

The phrase “but go off I guess” comes from Tumblr. It’s usually used after contradicting someone or calling them out. It can be meant seriously or sarcastically.