In response to FFF's post - I think argument about the point is largely irrelevant. If someone is issuing useful information about the airfield, who but an idiot would not comply?
Would anyone ignore anyone who said "go-around" on the basis that the airfield is information only, and that no instructions are issued??
Easy answer is to find out what info is available on the radio, and what regular users of the airfield expect people to do in response. While it may not technically be an instruction (but instead is a request for info) to "report downwind", common sense means that you should be replying when people expect you to do so!!