Well, it depends on where you are.

As far as I know, where I have lived most(Western Australia) it is not considered vandalism.

This is the third result on Google for "vandalism chalk"(though it seems to have some mixed messages):

https://itsartlaw.com/2013/09/02/california-court-rules-that...

That still results in a physical change to the building, even if it is only temporary (or not, if the building material is unusually porous).

The test that I remember seeing applied in the past concerns "intention distruction or defacement". As I understand it, alterations (graffiti, breaking a window, removing ornamentation, etc.) that alters the physical object or space can apply.

You're using the word in a different sense than the person you're responding to. They're talking about the standard for charging someone for a criminal act.

Possibly not, but you would be in violation of trespass, which is somewhat ironic given the article's failure to prevail on a trespass claim.