Flushing the toilet when there's nothing in it but differently coloured water is a waste, but I understand why you have to do it in a social context. I would prefer not to needlessly strain my shitty pipes, but I prioritise other people not needing to know that I piss just like they do.
Anyways, this is a very obtuse way of asking how many times does a person have to come to your apartment before you can shamelessly not flush the toilet after (visibly) peeing?
if it's your apartment it won't bother me too much. if it's mine I'll cut you down where you stand