I was indicating the side I was parked on.
I was indicating becuase I didn’t want someone to come along and not see me even though I was very visible I was being safe.
OK, maybe the guy was simply baffled by your use of the indicators (contrary to the Highway Code*) , and wanted to post it up on the internet for amusement.
* = Rule 103 "use them to advise other road users before changing course or direction, stopping or moving off", and "make sure your signals will not confuse others"
Rule 116 "Hazard warning lights. These may be used when your vehicle is stationary, to warn that it is temporarily obstructing traffic."