Why does "crossing the rubicon" mean something so immoral that you can never turn back?

It doesn't mean that. That's just a modern connotation because many people use(d) it in the context of morally dubious choices or with a moralistic lense while looking at complex topics like ancient warfare.

It was an act of war.
Like October 7th

>>24580639 (OP)
Because there are not that many situations these days where a conscious decision transforms you to the point where there's no coming back - which is the true meaning of the phrase. Moral decisions have that power.

>>24580661
What about choosing to come to 4chan

>>24580639 (OP)
its not about morality its just a point of no return

>>24580662
Crossing the Rubicon is usually reserved for a discrete decision you can pin-point and that cannot be taken back. You can come to 4chan but also leave it. You can increase or decrease your hours spent here. But for example sharing your personal information and passport photo on 4chan would be crossing a Rubicon, because it is a specific consciously decided event that cannot be taken back.

>>24580675
unless you write something genuinely disturbing (comments like "fuck niggers. lol." don't count.) no one actually cares if you get doxxed on 4chan. Just look at Bradley Hargreaves for example.

>>24580701
You might care, you might not, depends on your situation and how 4chan is treated in the media cycles, but it's a specific decision that cannot be taken back.

>>24580675
>you can leave
lies

>>24580701
Ewww, Penrith.

>>24580639 (OP)
https://penelope.uchicago.edu/Thayer/e/roman/texts/plutarch/lives/caesar*.html
Roman armies were supposed to stay out of Italy. The Rubicon was the boundary with Gaul. Caesar crossing the Rubicon was seen as a direct attack on the Roman people and their Republic.