"I took it home with me yesterday and woke quite miserable this morning. Will make sure I leave it behind this afternoon," another one said.
"I'm sure that I'm never thrown anything that I can't handle, so although it will be a tough trial, I will learn and grow from it," a third comment read.
The juror wrote on Wednesday - the jury's second day of deliberations - that it "[may be] over tomorrow".
The juror, who cannot be identified, did not discuss the evidence in the trial or the jury's deliberations.
Defence barrister Saul Holt QC argued for a mistrial but Justice John Byrne dismissed the application.
But he did scold the juror anonymously after the jury delivered its verdict.
"This is a particularly disappointing feature of the events of the day but only one is responsible for it," Justice Byrne said.
"That juror will discover when [they] accesses [their] Instagram account that many members of the public have commented on [the juror's] decision to communicate with others during the course of the trial."