Posts about cars for sale breach the rules of posting?

[Horsey McHorseface]

This is the email I received from PH:

Your reply to the topic 'I got another shed.' has been removed for the following reason:
Posts about cars for sale breach the rules of posting. Your post has been deleted. [end]

The OP of that thread is neither a friend or family. Precisely which rule did I break?

https://www.pistonheads.com/gassing/rules.asp

My posted link was no different from the hundreds posted in the Bargain Basement thread.