conversational drift 

The path of a conversation that takes an abrupt turn from the beginning of a thread to the end of a thread.

conversation, conversational, drift, ass, comment

Amanda: If you want to be well liked post something about getting things shoved up your ass.

...several people contribute comments. to a very different last comment of,

Roman:Do you love how this went from getting things shoved up your ass to getting an MBA?
...this is "conversational drift"

conversation, conversational, drift, ass, comment

conversational drift by Fano Boss February 4, 2012

Conversational Drift 

When a conversation in a text chat or irl gets way off track

Jake: and that’s why I can’t trust someone who likes pineapple on pizza!
John: true lmao, we had some real conversational drift here. Got way off our topic of The Florida trip

Conversational Drift by Golden Spider June 12, 2019