As far as I know there is nothing halachikly wrong with someone in Israel posting while it is still Shabbos in NY. The mods won’t approve it until after Shabbos wherever they are though.
Australia is about 15 hours ahead of NY so it makes sense that someone with an Australian IP is posting around 9am Saturday NY time since Shabbos is over by then. But it seems to me that this same prolific poster of many screen names is also posting at the same time on Friday morning when it should be past Shkia in Melbourne.