Well, yes, but that's not relevant for a very simplistic idea of the motion of a galaxy. A singular reddit comment is not comprehensive and would take far more baseline knowledge to promote that sort of understanding.

For the average person they don't know and don't care about that smaller detail.

It's interesting and intuitive but relatively non-obvious. The galaxy operates with the same physics as the galaxy. Planets closer to the sun orbit faster than objects further out. So too are the objects near the center of the galaxy orbiting faster than those objects in the outskirts.

Edit for visibility: This is meant as a simple explanation and not a comprehensive one. There are far more details about the movement of things in the night sky than what I would expect anyone to know of or understand. Please take this for what it is - a very simple illustration - and not an absolute truth.

It's important to note that "Australia" in this case refers to Gondwanaland. This was the Southern supercontinent that includes what is now Australia.

I, too, am become tree.